The Doctor darted around the console to reach the communications console. It was bleeping urgently, indicating an emergency communication.

“Where’s it coming from?” Susan asked.

“Titan,” he answered. “The moon of Saturn.”

“Professsor Marius?”

“No,” The Doctor read the message. “It’s from Ric!”

“Ric? The little robot? He sent you a message? An EMERGENCY Message.”

“Yes.” The Doctor’s face was pale as he read the content of the message. “He sent a message to me to tell me that The Professor is DEAD!”

“Oh,” Susan gasped. “Oh no, oh no. He was a NICE man.”

“A very nice man,” The Doctor said. He moved over to the navigation section and keyed in the co-ordinate for Titan.

“Who would kill him?”

“It doesn’t say he was killed. It could be natural causes.”

But The Doctor looked as if he knew it wasn’t. Susan moved closer to him. She put her hand over his. He looked at her and smiled.

“All these years, I should be used to people I know dying. But I don’t think I will. At least not until it’s me they’re burying.”

“That’s how it should be. Makes you Human, or… or whatever it is you are.”

The Doctor smiled. She knew what he was, of course. He had told her all about Gallifrey and the Time Lords in one of the quiet times between materialisations when there was nothing to do but talk to each other. But sometimes it was a bit too big a thing to deal with. He was an alien from so far away from her own planet that she had no mental faculty to imagine it.

“We’re materialising,” he said. “Come on, let’s find out what happened.” He reached out his hand to her. She took it. She always did. Whatever she thought he was, she wanted to be with him.

Titan was not an especially hospitable place even in the year 10,098. It was still necessary to stay within a protective dome where there was a breathable atmosphere and gravity set to the level humans prefer. The TARDIS landed in the private vehicle hangar bay. After his psychic paper was examined at the arrivals desk The Doctor and Susan were passed through to the bright, welcoming reception centre. The Doctor immediately went to the information kiosk to ask about The Professor.

He was extremely puzzled when he returned to where he left Susan on a comfortable hospitality sofa, watching the latest news around the solar system, presented by people so insipid about the events they were reporting that they could have trained in the 21st century on Newsround Extra.

“What is it?” she asked as she followed him into a turbo transporter. It was like a lift with comfy seats that went sideways as well as up, taking them to the right location in the thirty miles wide habitat with the minimum legwork.

“I’m not sure,” he answered. “I think… I’m certain the TARDIS brought us to the right temporal location, but….”

He shook his head, because even his brain was having trouble with what he had just been told. He thought it had to be a mistake, but if it wasn’t….

The turbo transporter brought them almost to their destination. They walked the rest of the way down a long ‘street’ with a glass roof looking out on the Titan sky. Susan tried not to be distracted by it, because it was a busy street with people coming and going and The Doctor teased her about obviously being a tourist. She looked instead at the houses either side of the street. They looked almost like semi-detached Earth houses except they were all made of some sort of white material and had flat roofs. They all had small gardens with gates and plants growing in them.

“Lovely,” Susan declared. “Home from home.”

“Yes, the residential area is nice,” The Doctor admitted. “Although I do get an old Earth song in my head…. The one about little boxes made of tickytacky that all look the same.”

Susan laughed.

“My mum used to sing me that song when I was little. Where did YOU hear it?”

“Jukebox in the Beta Zeta spaceport when I was a teenager. My TARDIS was broken down and I had to hang about for a part to be delivered from home. I learnt the whole history of late 20th century Earth popular music while I was waiting. I loved the 60s, 70s, even some of the 80s, but the 1990s were DISMAL.”

Susan laughed again, then felt guilty about it since they were going to find out how Professor Marius died. But when she said that The Doctor shook his head and became quietly puzzled again.

She began to understand when they came to the right house.

“But…” She stared in surprise as The Professor, looking alive and well, tended his garden while Ric rested peacefully on the lawn. Neither noticed them until The Doctor opened the gate and stepped onto the path. Then Ric looked up like a sleepy dog and glided towards them.

“Mistress Susan, Master Doctor,” he said in his mechanical voice that reminded The Doctor of a laid back Dalek and reminded Susan of Zippy from Rainbow. The Professor looked up from his weeding and smiled broadly as he dusted his hands off and came to greet them both enthusiastically.

“Lovely to see you both,” he said. “Come in. I’ll have tea in a jiffy.”

“I prefer mine in a cup, thanks,” The Doctor replied. It was all he could think of to say. He had been prepared to visit a house of death, people mourning, maybe a police investigation. But when he inquired he had been assured that The Professor WAS alive and well and living comfortably in the residential area on the south side of the habitat.

“Well,” Susan told him as they waited for The Professor to bring in the tea from his kitchen to the nicely furnished drawing room that could easily pass for 21st century Earth. “He’s alive. That’s good, isn’t it?”

“No,” The Doctor answered. “I mean… yes, it’s good. But it’s wrong. We were told he was dead. Something is…”

Ric hovered past. The Doctor reached out a long leg and halted him.

“Master Doctor…”

“We’re going to have to talk about this Master Doctor thing sometime,” he said. “But right now I’ve got a more important issue with you. Ric… have you brought me here under false pretences? You sent a message to say The Professor was dead…”

“That is correct, Master Doctor.”

“Well he doesn’t look dead to me. So what’s going on, Ric?” Then The Doctor’s face seemed to darken with anger. He grabbed Ric tightly and his eyes fixed on the eyelight of what passed for a face on the mechanical unit. “NO!” he cried out. “NO! You sent the message with a retrospective time-space co-ordinate so that we would arrive BEFORE it happened. But if we stop it happening, we cause a paradox, because then you won’t have sent for us, and you CAN’T stop people from dying if they’re meant to die, and….”

“But it can’t be that, Doctor,” Susan pointed out. “If this is an earlier time, then Ric won’t KNOW that anything is going to happen. He’s not a psychic robot! And he admitted to sending the message.”

“Oh!” The Doctor’s anger subsided as he realised Susan was right. “Er… Sorry, Ric.” He put him back down on his hover pads.

“No apologies necessary,” Ric answered. “I have no offence to take.”

“Yeah, that’s what K9 used to say, too. But, if it’s not that, what’s going on, Ric?”

“Is everything all right?” The Professor asked as he brought a tea tray into the lounge.

“Everything is fine,” The Doctor assured him. “Except….”

He watched as The Professor poured tea for them all. He offered biscuits around, too. Susan took one. The Doctor sipped his tea, but he was obviously agitated still and biscuits were a distraction, along with The Professor talking about how he rather enjoyed making home made biscuits now he was semi-retired. Apart from the appalling image of a great scientific mind like Marius pottering about a ticky tacky house making biscuits, he still had the big question to answer.

“Ric sent us a message to say that you were dead,” The Doctor said at last.

“Oh, I see!” The Professor nodded in understanding. “That explains why you’re so upset.”

“It was just a mistake then?” Susan asked.

“No, he WAS correct,” The Professor answered. “I’ve died 3 times this week. Very annoying.”

“Come again?” Susan looked startled. So did The Doctor.

“Professor…” The Doctor looked at him in astonishment. But for once words failed him.

“I will explain,” he said as he sat with them. “I would be dead altogether but for my own inventions. The synthetic body. Wonderful idea, if I say so myself.”

“Professor? You’re not making any sense, you know. Can you start at the beginning?”

“Certainly,” he said. “It begins with my research into artificial intelligence. You know how I have dedicated my life to such things. K9 and Ric are my more simple designs. But I have worked for a long time on a realistic cybernetic body. And you can see how successful that has been.”

“What?” The Doctor reached out and touched The Professor on the arm. He felt for a pulse. There wasn’t one. There was some kind of electronic impulse, but not a PULSE of a living body. “This is an artificial body?”

“I was dying,” he said. “Even before you rescued me from B’Tallia Vance’s clutches, I knew there was a problem. Cancer, you know. One of the things we’ve NEVER been able to cure. But I had the prototype almost ready. I worked so hard in the last weeks, knowing my flesh and blood body was breaking down. Finally, when I knew I had only days left, I downloaded all of my memories to the prototype and let my old body go. So here I am, all that I ever was, my memories, my knowledge, in a new body. It’s nearly twenty years since I made the transference and until just recently I never have any trouble at all.”

“Twenty years?” Susan looked at him and realised two things. Firstly, that an artificial body wouldn’t age, and secondly, that twenty years was nothing when you travel by TARDIS.

“Professor Marius is dead?” The Doctor was fixed on one point. “Marius… my friend… died?”

“No,” The Professor insisted. “I am Marius. I am alive. In this copy of my original body.”

“No,” The Doctor said. “You are… You can’t… you should not have….”

“Doctor…” Susan wondered about his reaction. “Doctor what’s the matter?”

“This is wrong. Artificial life, yes. K9, Ric, even lifelike robots, as long as they are programmed to know they ARE robots.”

“Yes,” The Professor said. “YOU helped forge the Galactic Treaty that granted rights of existence to such lifeforms.”

“The Treaty of Ux,” The Doctor replied. “Yes, I did. It was to ensure that sentient lifeforms were not used as slaves. But what you have done… to put a Human mind into an artificial body…. It opens up a whole new ethical issue. It is… it is only one step away from stuffing a Human brain into a metal shell and creating… a Cyberman.”

“Cybermen have no control of their brain functions,” The Professor countered. “They are emotionless monsters. This is different. I sought a way to continue my life beyond my natural span. That is all.”

“Nobody should outlive their natural span,” The Doctor answered. “I am sorry… cancer is a terrible disease. A painful death… but The Professor should have accepted his fate.”

“Doctor,” Susan reached out to him. “You’re talking about him as if he isn’t here.”

“He’s NOT,” The Doctor snapped. “This is NOT The Professor. This is a machine… a walking computer… with The Professor’s memories on a chip.”

“But it’s STILL The Professor in a sense. Surely… Doctor…. Isn’t it an amazing thing The Professor has invented? He didn’t have to die. His life, his work, continues.”

“Does it? Is the computer mind capable of learning and stretching itself? Of discovering new things? The Professor’s mind is PRESERVED, that’s all. Preserved like an artefact in a museum, never to change and expand.”

“Yes, it does,” he answered. “I have all the mental faculties I ever had. I am fully capable of continuing my work. I do less work at the research laboratory now because they SAY I am too old. But I continue my experiments in my own workshop. I have patented over 700 new designs since my first ‘death’, all of immense benefit to mankind.”

“Doctor....” Susan looked at him, then to The Professor – or what SEEMED to be The Professor. She wasn’t sure any more. What The Doctor was saying made a sort of sense. But so did what The Professor was saying. She thought of some of the people she had known, even in her relatively young years, who had died before their time. If their minds could have been transferred in this way, if they could have gone on living a sort of life….

“No,” The Doctor insisted. “It is wrong. Everything and everyone must die eventually. Nobody is immortal. Not even me. This ISN’T right. If I had known what you were researching, Professor…/”

“What?” Susan asked him. “You would have stopped him? Killed him? And what gives YOU the right to decide that? You’re NOT his superior. You don’t rule him. I understand that you don’t like the idea, but it wasn’t your decision, it was HIS. And he is STILL your friend. So… so please forgive him, Doctor, and don’t stop being his friend.”

The Doctor looked at Susan. He was on the point of dismissing all she had said, telling her she was young, she was from the 21st century, she didn’t understand the issues involved. Then he realised that she DID understand them, and for all his ethical issues, what she had said made perfect sense.

“Marius,” he said. “I am sorry for my rudeness. Please accept my apologies.”

“Think nothing of it, old chap,” Marius answered. “Please, take more tea. And DO try a biscuit.”

“I think the tea is going cold,” The Doctor replied. “Besides, there is another detail I was deflected from here. You said….”

“He said he had died three times already this week,” Susan finished for him. “That’s the reason Ric called us. Because THAT is weird. Even more weird than The Professor being a robot. But you weren’t listening because you have a hang up about Cybermen, whatever they are.”

“Yes,” The Doctor said, seeming to come to his senses at last. “Yes, you’re quite right. Perfectly right. Professor… please… tell us what happened.”

“Well, I don’t know for sure. Only that three times this week I have been doing perfectly ordinary things – walking in the market place, tending the garden here at home, travelling on a turbo transporter – and my brain has been subjected to a localised EMP burst and shut down. I am only here to tell the tale because my colleagues from the laboratory reprogrammed the brain chip with my back up memory from the sentience crystal.”

“The what?”

“Another of my inventions. A copy of my entire brain, with up to the minute memories, is stored in the crystal - like a back up copy of computer programmes. I download it every evening, last thing at night, so all my most recent memories are saved.”

Even Susan understood that. It literally WAS like saving everything on a computer to a backup drive.

“But when you’re ‘killed’, you lose everything you’d done after the last back up?”

“That’s correct,” he answered her. “I have had three whole days of my life wiped out. The last time was the most worrying. I had been working on an important piece of work at the laboratory. I am almost certain I was on the verge of a great discovery, and it was all lost.” He smiled as Susan opened her mouth to speak. “Yes, my dear, you are quite right. I SHOULD have kept written notes of my work. But I have never worked that way. It is all up here.” He tapped his head as he spoke. Susan smiled. The Doctor did, too.

“In future, try writing things down the old fashioned way.”

“I haven’t done that for a long time,” The Professor answered him. “I’m not even sure if I own a pen!”

“I’ve got a big bag of them in the TARDIS,” The Doctor said. “I’m always picking them up, here and there,” he added.

“I never figured you for an Argos shopper,” Susan grinned at him. “But is that the only advice you have for The Professor? Carry a biro?”

“Of course not,” The Doctor answered. “I intend to get to the bottom of this. A good old fashioned bit of investigating. Just the thing. The Doctor and Susan on the case. I think we’ll start tomorrow with a good old fashioned snoop around your laboratory, Professor.”

“Then let me extend my hospitality to you both in the meantime,” The Professor said. “You are welcome in my humble home.”

Despite his earlier reservations, The Doctor accepted his offer and Susan noted that the two of them seemed much friendlier now. It was so unusual of The Doctor to be that vehement about something.

Or perhaps it wasn’t, she added, reminding herself that she had known him for only a very small fraction of his life. She hardly knew a fraction of the troubles that afflicted his soul.

After a very good supper and a glass of The Professor’s home made wine, which was, as far as she could tell, very nice, she wandered into the garden. The Professor was not the only artificial thing on Titan, she had soon realised. It was, after all, just a rock so far out in space that even the side that faced the sun was neither warmed nor lightened by it. The day and night within the habitat was completely simulated, using, The Doctor explained, photo-sensitive cells in the exo-glass dome. There were twelve hours of darkness, twelve of light. A dusk period saw the lights dim into the night ‘sky’ dotted with a representation of the real sky outside.

“It’s very pretty,” she said to no-one in particular. “But it’s not the real thing.”

And that, she supposed, was The Doctor’s problem with the cybernetic Marius. He wasn’t the real thing.

He had no problem with robots. He spoke lovingly of his old robot dog given to him by Professor Marius. He liked Ric. But robot and Human combined bothered him. It was neither one thing nor the other, she supposed.

She turned a corner and saw The Doctor and Marius sitting on the patio in the back garden with more of the home made wine. They were talking quietly. She knew she shouldn’t eavesdrop, but she was interested in what the two had to say to each other.

“I should remember,” The Doctor told him. “That you saved my life all those years ago when the Swarm Nucleus tried to use my body as its incubator.”

“How long has it been?” The Professor asked.

“For me… about two and a half centuries,” The Doctor answered. “For you… it must be forty years. More, perhaps.”

“Two and a half centuries!” The Professor smiled wryly. The Doctor noted the expression.

“Yes, you’re right. My concept of life is different to yours. I come from a race that is happy to face the oblivion of the grave after two or three thousand years of life. We are afflicted by very few illnesses. It is hard to understand that others, with life spans measured in decades, not centuries, might feel they have the short end of the stick.”

“That is why, when I knew I was dying, I thought this might be the answer.”

The Doctor said nothing. Marius refilled his glass for him and sat back, looking up at the artificial stars.

“You know, Doctor,” he continued. “I think I understand YOU much better for this.”

“How?” he asked.

“To die… painfully… And then to live again… with the memory of that death….”

“Oh.” The Doctor looked up at the artificial stars, too. He still couldn’t think what to say.

“Immortality has a price. One almost too hard to bear.”

“Yes,” The Doctor said with the weight of experience in the single word.

“How do YOU bear it?”

“I know the universe still needs me in it. That I have reason not to stop living,” The Doctor answered.

“And if the time comes when that is no longer true?”

“Then I should be glad to join my ancestors in the peace of the grave. I don’t wish to live a moment longer than is my right. But that is easy enough for me to say when I have at least another thousand years to live.” He paused. “I was too hard on you, Marius. I was applying my own morality, my own standards. I forgot to see it from a Human point of view.”

“But you still hate what I have done?”

“I fear the consequences of it. The man who devised the Cybermen wanted much the same as you – to extend his own life. He almost destroyed the Human race. This… if it went beyond the prototype… who would be deemed worthy of living on in one of your cybernetic bodies? The greatest minds? The scientists, artists? But I think the more cynical side of Human nature would prevail. Your invention would end up being a luxury of the superrich. Those who could afford it would have the chance of immortality. And they would be far from the greatest minds. The most ambitious, the most ruthless, more like. I’ve seen what happens when ambition and ruthlessness are allowed the sort of power this affords them.”

“Doctor,” Marius answered. “I give you my word, this prototype will be the only one. I will not be the progenitor of a master race such as you envisage.”

“And suppose somebody uses your blueprints, copies your idea?”

“The blueprint is in this mind,” he assured him. “Nobody can take it.”

Susan listened to the conversation quietly. The Doctor’s mood was a strange one, she thought. He really DID seem as old as he said he was as he talked.

She hoped he would shake off that mood. She much preferred the smiling, devil may care, energised Doctor, rushing headlong into trouble and solving the problem by the skin of his teeth.

Even if that was a front that hid this older, more world-weary Doctor from the universe.

A noise behind her distracted her from her thoughts. There was somebody else concealed in the darkness, watching The Doctor and The Professor.

She heard a click and a whirring noise that she instinctively knew was wrong.

“Doctor!” she screamed out loud. “Professor! Get down!” She ran towards them, throwing herself on the ground as she heard the powered up weapon discharge. She saw out of the corner of her eye The Doctor step in front of The Professor as some kind of electronic ray enveloped them both. She heard The Doctor yell and The Professor cry out in pain and disappointment. She saw The Doctor lay The Professor down on the ground gently, then he was up on his feet, vaulting over the rose bushes that flanked the patio and giving chase as the assailant ran into the night.

Susan stood up and went to the Professor. Ric was hovering beside him making mechanical noises that sounded like a dog worrying about his master. He looked dead. Or… switched off at least. His eyes were staring up at her in an eerie way and the artificial flesh was cold to the touch.

She didn’t know what to do. If he WAS still Human she would have done CPR, but that was obviously useless on an artificial life.

Besides, from what he had said earlier, it WASN’T the end. It just meant that they had to revive his memory.

She looked around as The Doctor returned. He looked, despite the urgency of the situation, almost cheerful. The thrill of the chase, literally. It energised him.

“I lost him,” he reported. “He reached the turbo transporters. I did get a trace on his destination, though,” he added. “The answer to this mystery definitely lies in the professor’s laboratory.”

“The professor’s dead,” Susan told him. “Again.”

“I know. I felt it. It went straight through me. A localised EMP. Very localised. Ric is fine. It just fried The Professor’s micro brain.” He bent and lifted the body into his arms, quite gently. “All right, my friend. You know I don’t like this, but I’m playing it your way.” He looked around and whistled low. Ric came to his side.

“Ma….” He began but The Doctor nudged him with his foot. He stopped.

“Just show me where The Professor keeps his back up memory,” he said. Ric whirred in reply and went into the house. They followed him in through the lounge and through the hall to a door that opened with a numeric keypad and a palm print activation.

“The code is 45257809,” Ric said. “And The Professor’s handprint…”

Susan keyed in the number then The Doctor held The Professor’s hand to the palm print reader, marvelling at how accurate he had made his prototype.

“The artificial skin was the work of Professor Ralph Noae,” Ric explained as they descended to the basement by a set of steep steps. “The second greatest scientific genius, after my master, Professor Marius.”

“Listen, you,” The Doctor said with a laughing tone in his voice. “Rankings of scientific geniuses don’t count when I’m in the room. They ALL come second. But I should have guessed as much. Noae is the man for that sort of realism in artificial lifeforms. But the mind transfer - that’s right up Marius’s alley.”

“I do not believe the professor owns an alley,” Ric answered.

“He owns a private laboratory that would have made Doctor Frankenstein weep!” Susan noted as she reached in the usual place and found a light switch. The Doctor crossed the room at once and placed Marius’s body on the table that was clearly meant for such a purpose. He secured the arm and leg restraints and attached the wire helmet to his head. Micro probes automatically bored into the forehead to transfer the data.

“All that is fairly obvious,” The Doctor said. “But what next?” He looked at the computerised control and the memory crystal the size of a small melon that lay within a protective dome. Even he, for all he had said about genius, wasn’t sure what he ought to do, and he was hesitant to try. Visions of The Professor being zapped by thousands of volts of power and turned into melted plastic flashed before his eyes. “Ric, do you know how it works?”

“Yes, Master Doctor,” he answered. “I have observed Professor Nigle performing the procedure.”

“The Professor’s assistant?”

“Correct.”

“Well, he’s not here right now, so talk me through it.”

Being talked through a procedure by a voice like Ric’s was not the most aesthetically pleasing hour he had ever spent, but it was the only way. At last, the crystal activated and he saw activity on the scanner monitoring the micro-brain of the Professor’s synthetic body.

“Professor,” he said gently as the procedure finished. “Wake up old boy.”

The professor’s eyes opened. He looked at The Doctor and frowned.

“When did you get here?” he asked.

Of course, Marius had lost everything since his last back up. That included, The Doctor realised, the row he had with him about what he had done.

“Good,” he thought. “Let’s start again, without the bitterness.”

“I came to see you this morning,” he answered. “But you don’t remember because we had to restore your brain again. You’ve lost another day. I think that makes four of them now. You were telling me about it.”

“Oh, dear. Again?” The professor looked worried. “This is becoming most inconvenient.”

“This is becoming dangerous,” The Doctor insisted. “You need help, old man. Just as well I’m here.”

“Doctor!” Susan interrupted him. “I heard a noise upstairs.”

“You look after the Professor,” he said. There’s still a lot of gamma energy that needs to dissipate before I’m ready to declare him up and about again. Ric, come with me. In silent mode, please.”

He held the sonic screwdriver like a weapon as he stealthily climbed the stairs. There WAS somebody else in the house. He could sense a presence. He moved quietly through to the hall. Somebody was using a torch in The Professor’s study.

“Drop that and put your hands up,” The Doctor demanded. The man dropped the paper copy of some kind of blue-print and did as he was told. It was ALL in the tone of voice, The Doctor thought with just a little smugness. He SOUNDED as if he had a weapon. But except in welding mode the sonic screwdriver was as lethal as a jelly baby.

“All right, turn around and identify yourself.”

“I’m Professor Nigle,” he answered. “I’m Marius’s assistant. He’s been hit again, hasn’t he? It triggers an alarm. I came to him as fast as I could. Who are you, anyway? What have YOU done with him?”

“The professor is safe,” The Doctor answered. “He’s just coming round from his procedure. But if you are the one who usually helps him, why are you nearly an hour late and what are you doing in here? You know where the laboratory is.”

“I…” Nigle looked at The Doctor and abandoned his answer as he tried to make a run for it. He never even got to the door. Ric glided into his path, tripping him up. The Doctor grabbed him firmly before he hit the ground. He fought only briefly before The Doctor administered a Malvorian pinch to the neck that rendered him semi-paralysed and very docile. A quick search of his pockets located the EMP gun. The Doctor discharged it safely out of the window.

“You sent an empty transporter and doubled back? Oldest trick in the book and I fell for it. Except I took a judgement call and came back to The Professor rather than going on with a chase across the habitat.”

“It would have worked if….”

“If it weren’t for those kids and that darned dog?” The Doctor laughed. Nigle looked blank. The cultural reference was lost on him. “Famous last words of ham-fisted bad guys the universe over. You’re going to jail, Sonny Jim. But first I want to know what you’re up to. Ric, guard mode, if you please.”

“Yes, Master Doctor,” Ric answered and dutifully stood over Nigle, his eyelight flashing menacingly. The Doctor, meanwhile, picked up the documents that had been dropped. They WERE blueprints. They were the plans for Marius’s own cybernetic body, brain chip, the formula for the artificial skin and the construction of the back up memory crystal.

“So it wasn’t in his mind after all. He DID keep hard copies! And you were stealing them?” The Doctor turned to Nigle as he sprawled on the floor. “Why?”

“Why indeed?” Marius’s voice asked and The Doctor glanced up to see the old man standing there with Susan holding his arm as if he was still a little unsteady.

“For money, obviously,” Nigle retorted. “Have you any idea how much some people would PAY for a system like this? I have contacts…. Rich men and women who would make ME rich so that they can live on after their natural deaths.”

“Is one of them called Cassandra?” The Doctor asked. “How many times has it come to this? Money? YOU were prepared to kill your friend for MONEY.”

“He wasn’t killed. I just neutralised his brain while I worked out how to get into the safe. I had to get a copy of his palm print and then find the combination of the lock.”

“Four times?”

“It was a very good lock.”

“My invention was for the benefit of mankind, not for rich men to stay alive and get richer. I meant it to be a way to preserve the greatest minds.”

“Your invention is going to make ME rich,” Nigle said and he rose from the ground, despite being in some obvious pain from The Doctor’s restraining force. He grabbed The Professor by the neck and at the same time reached in his pocket and pulled out what was obviously a small hand grenade. “I don’t need the blue prints if I have the prototype.”

“Put that down, you foolish man,” The Professor demanded.

“I don’t need you ALIVE to retro-engineer the process,” he added. He shifted the grenade to the hand under The Professor’s neck while he snatched the EMP gun from the Doctor’s pocket faster than even he expected him to move. He pressed it against The Professor’s head and Susan screamed as she saw Marius’s eyes go blank again. Ric howled in grief as he saw his master ‘die’ yet another time.

“Shut up,” Nigle yelled at them both. “You two, whoever you are, walk in front of me, where I can see you. You, girl, get hold of that stupid tin thing or I’ll blow it to smithereens.”

“Do as he says for the moment,” The Doctor told Susan quietly. “That’s a thermite grenade. If he drops it we have 15 seconds until this house explodes.”

Susan took hold of Ric as he hovered by her side. She and The Doctor walked backwards slowly in front of Nigle, his eyes glued to the grenade that he held against Marius’s head.

Even with a time fold, he could only delay the detonation for a little while, he calculated. There was nothing he could DO for the moment but obey.

But taking orders was not something The Doctor had ever done well, and he certainly didn’t mean to do so for long.

He just waited for his chance.

They were all outside under the artificial sky. Nigle dropped The Professor’s lifeless body and turned. Before anyone else could move he had lobbed the grenade at the window of the Professor’s study where the blueprints were still in a heap on the desk.

“Like I said, don’t need the blueprints when I have the prototype,” Nigle said with a sneer as the study exploded into flames.

“The memory crystal!” The Doctor gasped as he watched the fire begin to spread.

“You’ve murdered him for good!” Susan screamed and launched herself at Nigle. It was an impulse driven by her sense of right and wrong and her fondness for the professor. It gave her slight figure enough impact to knock Nigle to the floor. “Give me something to tie him with, Doctor,” she said as she pushed the struggling man back down. “Doctor?”

“He went into the house,” Ric answered her. She looked up to see a blur as The Doctor ran in through the front door in a time fold. Ric moved towards her. She was too worried about The Doctor to take in how many pounds he was telling her he weighed with his gravity field switched off, but she got the idea. He sat on Nigle’s back and Susan was able to stand up.

She was standing alone in a scene of devastation. The Professor’s still body lay next to Nigle as he struggled and protested. The house was an inferno.

“Doctor!” she sobbed. “Oh, Doctor!”

There was the sound of sirens. She looked around at the street, expecting to see a fire engine. But this was not Earth in the 21st century. It was Titan in the 101st century. The engines came from above, fire hoses controlled by firemen with hoverpacks on their backs tackled the fire from the roof down. Meanwhile two police hover cars descended.

She was so astonished by all that, that she didn’t even realise The Doctor was standing beside her again until he spoke.

“Officers,” he said. “Arrest that man for arson, industrial espionage, possession of an illegal EMP pistol, and the murder of Professor Marius.” Again it was all in the voice. The officers did just as they were told. Ric drew back to let them. One of them turned and bent to look at the professor. The Doctor, his clothes smouldering slightly, and his face grimy with soot and sweat, passed the memory crystal to Susan, telling her not to drop it, and he bent and lifted the professor into his own arms. “We need transport,” he Again his tone made the police obedient to him. “To the hangar bay.”

“Hangar bay, sir?” The officer managed to ask, despite a strong feeling that it was a perfectly sensible place to go with a dead man and one who looked like he might spontaneously combust at any moment. “Isn’t the hospital a better idea.”

“Hangar bay,” The Doctor insisted. “As quickly as possible.” The police officer put his foot down and the hover car speeded up. But The Doctor was nervous. He glanced at the crystal in Susan’s lap.

“It’s damaged,” he said. “And the TARDIS computers aren’t compatible with it. I’m only half sure…”

“He might die for good?”

“Everything has it's time,” The Doctor murmured absently and turned his face away to hide the fact that he was blinking rapidly, trying not to cry.

“Master Doctor,” Ric said in a plaintive voice as he sat at their feet, more like a dog than ever. “Please….”

“Ric, you’re a mechanical lifeform, you’re not supposed to even know what ‘please’ means,” The Doctor told him.

“Please help my Master Professor.”

The Doctor didn’t answer. He couldn’t trust himself to speak. Susan reached and patted the mechanical creature reassuringly.

They reached the hangar bay in less time than it would have taken by turbo transporter, but it seemed, in their desperation, much longer.

“That’s because time is relative,” The Doctor said and in the back of his mind was a whole mad collection of pseudo-scientific/philosophic nonsense he could have added that would have raised a smile from Susan. But right there and then, as he cradled The Professor’s still form in his arms, that kind of wise-cracking daftness that had got him through all sorts of situations in the past, utterly failed him.

“Hangar bay, sir,” the officer said.

“Put us down next to the blue phone box,” The Doctor said. His Power of Suggestion was still working, at least. In a minute or two, when he was on his way back to his depot, the police officer would probably wonder why he had been acting as a free taxi service for their odd little group. But right now he was doing just what The Doctor wanted him to do. He landed the hover car right by the police box.

The Doctor gave Susan the key and she ran to open the door with Ric hovering alongside her. She pushed both doors wide open as The Doctor carried The Professor inside. Susan closed both doors behind her again as The Doctor lay The Professor on the floor beside the console. She noticed the police car leaving on the viewscreen as she brought the crystal and gave it to The Doctor. He opened up a whole section of the TARDIS console and pulled out wires apparently at random. Two of them he attached to the crystal, the others he taped, with bits of Elastoplast, to The Professor’s forehead.

“The crystal is BADLY damaged,” he said. “We have one chance. Susan… when I say go, press those two red buttons on the console.”

She stood ready, her fingers poised above the buttons. The Doctor himself knelt and put his hands on The Professor’s head, either side of his temples.

“I might be able to use my own body as a booster,” he said. “It’ll either work, or fry both our brains.” He looked up at Susan. “Now. Press the buttons.”

She pressed them. As she did, the crystal glowed red inside like a hot ember underneath still black coals on an open fire, and it smouldered as if it was cooking. At the same time, The Doctor stifled a scream of pain. She turned from the crystal and stepped towards him.

“No,” he warned her. “You really would fry. My body can take a certain… certain amount… pressure…. Aggh!” He shut his eyes as the mental energy contained in the crystal passed through him, using him like a conductor before it grounded itself in The Professor.

“Doctor…. My dear friend,” The Professor said, opening his eyes. “Oh dear. It’s happened again, hasn’t it?”

“Lie still,” The Doctor told him. “I’m afraid… I don’t think….” He looked up at the crystal. It was cracking and breaking. “I’m sorry, professor. There was too much damage to the crystal. The memories aren’t holding. You’re dying.”

“It was Nilges, wasn’t it,” he said. “I had a feeling about him. He kept wanting to know how much we could charge rich people to make themselves immortal. I kept telling him… not… not what it was about.”

“Nilges is explaining himself to the police,” The Doctor told him. “Your house… there was an explosion. Your blueprints, the basement… it’s all gone.”

“And I’m going, too.”

“I’m afraid so.”

“Oh, no,” Susan cried. “Doctor… please save him.”

“I can’t,” he answered. “I’m sorry. Ric, I’m sorry. Professor… I am so sorry.”

“It’s all right,” The Professor told him. “The experiment worked. I had more life than I would have had otherwise. But now….”

“Everything has its time,” The Doctor said. “Everything dies.”

“Yes,” The Professor agreed. “Doctor… this body… will you… take care… Don’t let it fall into the wrong hands.”

“I’ll do that,” he promised.

“Ric,” The Professor said, in a voice that was weakening. “The Doctor… will be… your master now. Be... true to him.”

Ric made a sound that could have been crying and then something like ‘affirmative’.

“Goodbye, old chap,” The Professor told The Doctor.

“Goodbye,” he answered, clutching at The Professor’s hand as he watched the eyes dim again. The electronic brain died. The mechanical heart stopped beating. The body stiffened.

“Doctor….” Susan knelt beside him, her head on his shoulder as he knelt there for a long time still holding The Professor’s hand. She was crying softly. He wasn’t though he wasn’t far off. He slowly let the hand go and turned and hugged Susan for a long time. He still didn’t cry. He let her cry for them both.

“We’ve got to be practical now,” he said after a while. “I’ll put the TARDIS into temporal orbit, and then we can… we can.…” He stood up and went to the console. Susan watched him operate the TARDIS.

“We could bury him in space,” she said. “Like burial at sea… They do that, don’t they?”

“No,” The Doctor answered. “Not for that body. An ordinary flesh and blood body, yes. It would desiccate and decay slowly, fall into the gravity of a planet and burn up. But that is the sort of technology that people like Nilges would be prepared to kill for. He told me to make sure that didn’t happen.”

“Not…” Susan looked at him in horror. “Doctor, not the trash compactor.” She knew there was a sinister machine in the corridor between the engine room and the kitchen that was perfectly capable of compacting The Professor’s cybernetic body into microscopic pieces and expelling them into space.

But….

“No, he deserves more dignity than that,” The Doctor promised her. He lifted the professor into his arms again and carried him. Susan and Ric followed. It WAS only a mechanical device, he told himself. The Professor – the REAL Professor, died twenty years before now and transferred his mind to this mechanical body.

He knew that. But even so, he felt he owed it to his friend to treat even his mechanical body with respect.

He brought him to the Cloister Room. Susan gasped in surprise when she saw it. She had never been in there before. There was no reason why she should. He had not needed to do any of his Time Lord rituals since she joined him.

“It’s beautiful,” she whispered. “Like a cathedral.”

“It serves a similar purpose,” he said tersely as they descended the steps to where the great Eye of Harmony lay under its well-cover. “Pull that mooring staff,” he said. “But mind your eyes. The reflection can blind Humans if they’re directly exposed.”

Susan pulled the heavy, ornately carved staff. A bright light shone from beneath it. As it did so there was a grinding sound that echoed around the silent room and the cover opened like a great eyelid to reveal what looked like a shining pool of mercury. She kept her eyes slightly averted from its dazzling light, but still it fascinated her.

“It’s pure artron energy,” he said. “The stuff that powers the TARDIS and courses through my body when I regenerate. It’s dangerous stuff. If you fall in, you’re a gonner.”

Susan stood back just in case. But she understood what The Doctor was going to do now.

“He’ll be a part of the TARDIS? Part of its power source?”

“Yes,” The Doctor said. “I don’t think he’d be unhappy about that.” He brought The Professor’s body to the edge of the well and keeping his own hands well clear he slid him into it. For a moment the body floated on top, and Susan half expected it to start to dissolve in front of her eyes like the cyborg in the furnace in Terminator II.

But it didn’t. It simply glowed with the same white light so that The Professor looked, for an instant, as if he was made of silver, then sank beneath the surface. It rippled for a few seconds more and then resumed its random swirling.

“Goodbye, Professor,” she whispered. Then The Doctor reached and pushed the mooring staff back and the eye closed. She felt his arms around her as she stood by the well.

“He’s gone, but we’ll always remember him,” he told her. “So will the TARDIS. She never forgets anyone.”

“So will Ric. He’s… he’s ours now.”

“Yeah,” The Doctor laughed softly. “The Professor always seems to dump his pets on me. I’m a sucker for it.” He laughed again, because it was easier than crying. “Come on, let’s find some planet where we can take a mechanical pet for a walk.”