He wasn't sure, but he thought Jackie's cooking might have improved a bit. Her attitude to him was almost mellow, too. He actually rather enjoyed the meal with her and Rose in the flat back in North London. He had brought a bottle of wine to go with it. The label showed it to be from a vineyard on Mars, bottled in the year 2354, and she accepted his assurance that it was a good year with something like a smile. Of course, alcohol didn't affect him, unless he allowed it to. He allowed it to affect him enough to warm him to the trivial conversation of the dinner and the sheer domesticity of the scene.

He smiled at Rose, for whom he made these sacrifices now and then, bringing her home to her mum and normality. She smiled back warmly and he knew that this was not going to be the day she would decide home was best and leave him. Every time they came back, there was that secret fear deep within him that she would choose to stay. One day, he thought with sinking hearts, she may do that. But for now she was still his Rose.

They were quietly drinking coffee after the meal when he told Rose he was going to talk to the boys and left the table. He stretched himself out on the long sofa and concentrated his mind on contacting his great grandchildren, 200 years in the future. He found them easily enough. It was break time at their school and they sat on the grass and made a pretence of playing a card game while they gave their attention to their great grandfather's lessons.

"Is he all right?" Jackie asked, standing over The Doctor as he lay there in deep meditation. "What is he doing?"

"He's fine," Rose said. "He's talking to the boys - Susan's twins. He's teaching them to be Time Lords."

"Why?" Jackie peered closely at the deathly still man lying on her sofa. She wondered what she would do if he WAS dead. Imagine having to call an ambulance for a dead man with so many strange things about him.

"So that he isn't the last of them," Rose answered. She sat on the edge of the sofa and held his hand. It WAS kind of creepy seeing him like this. Somehow in the TARDIS it was less weird. There he was part of the familiar strangeness. But on her mum’s sofa a deep meditative state in which she knew his hearts were barely beating and his lungs were still actually seemed really peculiar. “Make some more coffee,” she told her mum. “He likes a cup of coffee afterwards.”

Jackie went and made coffee. It was normal. Unlike what was going on in her living room. Through dinner she had managed to forget that The Doctor was not human. Even drinking Martian wine didn't disturb her too much after the first glass. But now he was doing weird, alien stuff again. And Rose was sitting beside him holding his hand. And the way she said, "He likes a cup of coffee afterwards," as if all this was normal to her. That was bizarre.

And yet, she thought as she stood at the kitchen door, Rose WAS happy with him. She clearly loved him deeply. And he loved her. Jackie knew love when she saw it, even if she didn't see enough of it for herself. And maybe that was half the problem. It wasn't that her daughter was in love with an alien, it was that her daughter was in love with the kind of man SHE, Jackie, had DREAMT of all her life; a man who could take her away from all of this and give her something better. Was she really just JEALOUS of them?

It was about ten minutes before The Doctor sat up on the sofa, apparently suffering no ill effects from the 'trance' or whatever it was. Rose immediately curled up beside him, her head against his shoulder, and he put his arm around her gently. Jackie brought the coffee through.

"So… what did you teach the kids?" she asked as she sat on the armchair at right angles to them.

"Advanced Theories of Thermodynamics. One of my favourite subjects."

"They're nine years old…" Jackie said, startled. "When we went shopping, I bought them Lego sets."

"Actually, I bought them," The Doctor said with a smile. "You and Susan did bad things to my credit cards that day. Yes, they're nine and they like Lego. But they're also Gallifreyan and they have the capability to learn beyond their Earth years."

"What is thermodynamics, anyway," Rose asked. "Sounds scary."

"It's the study of the properties of objects that create, transfer or are changed by heat," he said. "And it's part of everyone's lives. It's the reason these cups get hot when the coffee goes in, and why the top of your mum's oven is hotter than the bottom and why food cooks when you turn the heat on under the pan."

"I thought that was just cooking," Jackie said.

"Not the way you do it, mum," Rose told her. She remembered one bit about this subject that she knew. "First year general science. Three methods of transferring heart - conduction, convection and radiation."

"And the fourth - because I'm The Doctor and I bloody well tell it to," he added with a twinkle in his eye. Rose giggle, quite sure he could make elephants fly because "He bloody well tells them to."

"So that's the sort of thing you were teaching the boys?" Jackie asked.

"No, we're a lot further ahead than that. But science is just simple things at the basis. Nothing to be scared of. And you all know more of it than you think."

Strange, Jackie thought. He's so brainy, knows everything in the universe, and yet, he was actually sitting there talking about the thermodynamics of her oven in such a way that she didn't feel as stupid as he must think she was. He IS a nice bloke, she thought. A nice ALIEN? That still scared her a bit. Because she had met quite a few aliens for an ordinary woman from a London council estate, and he was the only one that hadn't tried to kill her so far.

The Doctor drank his coffee as he talked about simple thermodynamic properties of ordinary household objects. Jackie felt herself becoming interested despite herself. Then, suddenly, he faltered. His coffee cup spilled as his hand shook and he looked like somebody had stabbed him between the eyes.

“Hang on,” he said under his breath. Rose instinctively took the cup from him and he put the fingertips of both hands to his temples "Chris, Davie, calm down. Chris, just you, tell me again, QUIETLY." He was getting a message from the boys, and unlike their lesson earlier it was an urgent one. "All right," he whispered finally. "I'll be there ads soon as I can." And he stood up and looked at Rose. "I have to go," he said. "They need me. David…. their dad… has had an accident. He might be dying." Rose jumped up straight away and went to get her coat. Jackie, to his surprise, did likewise.

"There's room for another passenger in that box of yours isn't there?" she said. "Susan needs a woman to talk to at a time like this, not you, Doctor Christo Time Lord."

The Doctor looked at her for a long moment, then he nodded. "You may be right. Come on, then. But don't go getting space sick around my TARDIS or anything."

It was weird, Rose thought, her mum being there. It wasn't the first time she had been IN the TARDIS. She often hung around when it was 'parked'. But her being there as they travelled was weird.

"Why don't you two make some coffee," The Doctor suggested as he set the co-ordinates. "Rose, show your mum the kitchen. Rose had the feeling he really didn't want EITHER of them around the console room at the moment. He was obviously worried about Susan and David and the boys and didn't need small talk. She knew when to leave him alone just as much as he knew when she wanted to be alone with her thoughts. It was what made travelling in time and space possible without getting on each other's nerves.

"Good grief," Jackie exclaimed as she looked around the kitchen. "It's exactly like at home."

"The Doctor says the TARDIS is psychic and can make rooms look like I want," Rose said. "It does feel nice making meals in here for us."

"Do you have a bedroom?" Jackie asked.

"Yes. That's down the corridor. It looks just like my room at home." She didn't tell her mum that she never slept in that room. She was too afraid of waking and finding that the TARDIS and The Doctor and their life here was just a dream. She slept when she was tired on a pull out cabin bed in the console room which The Doctor, or Jack, when he was with them, considered a no-go area. The glow from the console was her night light, and the sound of the engines soothed her to sleep.

"And where does HE sleep?" Jackie asked.

"I don't really know. I'm not sure he does," Rose said. "He doesn't need sleep the same way. He does the meditation thing and stuff like that."

"So you never…"

"Mum! That room is a re-creation of the bedroom I have slept in since I was three. I'm not going to share it with anyone, not EVEN him. We DON'T. It's not like that. I… I love him, but it's not like that. Being with him, out here, is enough. We don't need anything else."

"Well, I'm glad," Jackie said. "Because I can't imagine how it would be - the kids you would have…"

"They would be like Susan's kids, I suppose. Really terrific kids. And we'd be happy. If it was like that. But it's not. So stop it." Rose made the coffee and they brought it back to the console room. The Doctor was busy over the glowing lights and buttons of the controls, but Rose was almost certain he was faking it. It onlytook a few minutes to set the co-ordinates for Susan's time. He looked up as Rose brought him coffee. He did look worried. Rose hugged him quickly.

"Thanks," he said quietly and he came to join Rose and her mum on one of the big sofas that they had accidentally acquired at the White House.

"How come this sofa has the presidential seal of America on it?" Jackie asked. Rose and The Doctor smiled.

"Very long story," Rose said. "We don't really have time to tell it. It doesn't take long to get to Susan's century."

"It helps that she lives in London," The Doctor added. "We're moving linearly in time without much of a spatial change. We're heading directly to the hospital, though. Susan and the children are there already." He looked worried again and lapsed into silence. Rose was surprised when it was Jackie who touched his arm gently and told him she was sure everything would work out. He looked at her gratefully before going to the console to guide the TARDIS to its destination.

He had got it exactly right, anyway. The TARDIS materialised under a quiet stairwell next to the hospital foyer. The three of them emerged and found their way to the intensive care department. As soon as they stepped into the waiting room Susan flew across the room and embraced The Doctor tearfully.

"Grandfather," she said. "I hoped you would come. I so wanted you to be here."

"The boys called me," he said holding her soothingly. "Of course I came. I wouldn't leave you at a time like this. My poor, dear child."

Jackie looked startled at the conversation between them, but her parenting instinct overcame her curiosity and she crossed the room to where the baby, Sukie, was crying in her carry cot. She picked her up and tried to soothe her. Rose went and sat with Chris and Davie, who clung to her tearfully.

Presently, Susan was called in to see her husband. The Doctor came to where Jackie was still trying to soothe the baby.

"Let her suck your little finger," he said to Jackie. "It's a Gallifreyan way of soothing babies. Doesn't work with humans quite the same. You don't taste the same, but it will act as a placebo at least." Jackie looked startled at that strange parenting tip but did as he said. The baby quietened immediately.

"What do you mean, we don't taste the same?" Jackie said as he sat down and the two boys climbed onto his lap. He put his arms around them both and cuddled them lovingly.

"Humans secrete excess salt through their skin. They taste salty. We secrete salt AND sugar. It tastes like honey. And the trick with the finger is an old, old way of calming babies where I come from."

"You never told me that," Jackie said to Rose.

"I never tried licking his fingers." Rose laughed at the very idea despite the tense situation. "And that wasn't in Jack's bumper book of Time Lord facts."

"And… anyway…" Jackie looked at The Doctor in an accusatory way. "Another thing. What did she call you when we arrived here just now?"

"Grandfather," he said with a sigh. They had MEANT to keep Jackie from knowing his exact relationship with Susan.

"When I first saw you with her… when her house was burned and you brought her to me to take care of… I thought maybe she was your ex-wife, that you still had a thing for…"

"I got the impression you'd jumped to that conclusion," The Doctor said.

"Well, Rose put me straight and said you were related. So ok, fair enough, I assumed she was your sister or something - after all she LOOKS about the same age you are. So that would be ok. That made you an uncle to the boys, and I thought you looked really good with them, how an uncle should be." She paused and looked at him. "But GRANDFATHER!"

"Yes."

"She is your granddaughter."

"Jackie… You have always known that I am much older than I look," The Doctor reminded her.

"Yes. I know. But still… I never realised what that meant. I mean… that means… The boys… You're their GREAT grandfather."

"Yes."

Jackie looked at him as he hugged the boys close.

"They love you a lot," she said. "Susan and the boys. It seems like you are a GOOD grandfather to them. I can't fault you there. But why did you keep that from me?"

"Jackie…" The Doctor reached out and took her hand in his, a gesture which surprised her. "Jackie, Rose tells me you're the kind of woman who gets confused programming the VCR timer. But I'm going to credit you with a bit more sense than that and tell you the truth. There are two good reasons why I never told you what Susan is to me - the first, and obvious, one is that the idea of a 950 year old great-grandfather in love with your teenage daughter was bound to give you cause for concern. It should. Because it has me worried, too."

"It does?" Jackie was surprised.

"Of course it does. I've been a parent. I've been through all the things you've been through, Jackie. Worried for my child's welfare. I know exactly how I would think if Rose was my daughter."

"Ok… but… Even so, you COULD have explained it to me. I might have been less worried..."

"Yes, I could. But the second and more important reason is that a few months ago in MY time I sat on your sofa over coffee and told you the whole story. But stupid me, I forgot that we were in 2012 when I told you. That conversation is years in the future still. And telling you again now creates a paradox. Not a dangerous one, not one that brings about the end of the universe, but a paradox still. Because a lot of things that happened since were as a result of that conversation and if it doesn't happen, they won't happen."

"I'm not sure I understand what a paradox is," Jackie said. "But… this conversation in the future…."

"Just try to remember THIS conversation Jackie - and when we do have that heart to heart in 2012, try to act as if this is all new to you. And I think we'll be all right."

"Ok," she said. "I'll try. But… ok… But… Susan. How IS she your granddaughter? How does it fit together?"

"She's the daughter of my son who died when she was a baby. I cared for her until she married David and made her own life here. She is my only living relative. Everyone else is dead. We're the last of our people born on our home planet. The children are a chance for us to restore our family line and make sure that the race of Time Lords don't die when I do. That's why I'm teaching them our ways."

"I think I understand," Jackie said. "That much I do. But… well, what SHOULD I do or think about a 950 year old great grandfather who is in love with my daughter?"

"I would hope, Jackie, that by now you would understand that my intentions are honest and accept it," he said. "It would mean so much to Rose."

Jackie looked at him and seemed unsure what to say in response. She was saved by Susan appearing in the waiting room again. She was crying softly and when The Doctor guided her to a seat beside Jackie and the baby she seemed numbed by her sorrow.

"He's dying," she said. "There was an accident at the laboratory. He took the full force of a radiation blast. It has destroyed his immune system and his whole body is shutting down organ by organ. Or it would be if he was not on so many life support machines. But… It's only a matter of time even so."

"Oh, Susan, I am sorry." The Doctor hugged her soothingly, feeling helpless. A feeling he disliked intensely. He had often been told he was a control freak - David had told him it more than once. And it was true. Moments like this, when he could do nothing, frightened him more than all the monsters in the universe.

"Can't they do anything?" Jackie asked. "Isn't this the sort of thing they do bone marrow transplants for?"

"Yes," Susan said. "But they'll never find a match in time. That's still as hard in this century as yours. He has a few hours at most."

"Ohhh!" The Doctor groaned and put his hands over his face. He stood up and walked across the room, stopping by the window and leaning his head against it as if the coolness of the glass was soothing some pain. Everyone turned to look at him. Rose was the one who reached him first and put a comforting arm across his shoulder.

"What is it?" she asked. He turned his head to look at her.

"It's down to me again," he said. "Totally compatible tissue - blood, heart… bone marrow."

"Oh!" Rose understood. In the past few months he had given so much of himself in very REAL terms. He had saved her life by giving so much of his blood it left him weakened for a time. He had given one of his hearts to Simon Gray, a man he didn't even LIKE to begin with, but who had put his life on the line for them all. Now he had it in him again to save a man's life by giving up what his own body was capable of replacing easily. "Well… you do WANT to don't you?" She asked.

"David and I have been at odds for a while. He doesn't really understand what I am doing with the boys. I don't think he approves of it. He wants them to be HIS sons, not mine. And the more I teach them, the more like me they are and the less like him."

"Yes… I know," Rose said. "But still… You wouldn't let him die when you could do something to stop it."

"You know me so well," he said with a smile. "You know I have no selfish motives."

"None at all," she told him. And he took her in his arms and held her tightly before going to Susan and putting the proposal to her that gave her a shred of hope where before it was hopeless.

"I didn't know that about us," she said when he explained. "But that means it doesn't have to be you," she added. "It could be me or one of the boys."

"No, it has to be me," he said. "I'd never put a child through this. And you have them to think of. They need you. I'm… expendable."

"No you're not." Surprisingly, Jackie was the one who said what they all thought. "From what I've heard the universe would fall to pieces without you."

"Well, the universe will have to manage to hold itself together for a while," he said. "My family need me." That seemed to decide the matter and he went to find the doctors looking after David to put his decision to them. Susan watched him go and cried even more loudly than ever.

"Forty one years - I didn't know was he alive or dead. When the twins were born, I so WANTED him to be there to see them. I had resigned myself to thinking he WAS dead, even though I was sure I would feel it somehow. Then he turns up… and we can't live without him."

"I can understand that," Rose said. "I can't imagine life without him, either."

"Yes, I know. But…." Susan looked at Jackie holding her youngest child, soothed by sucking on her little finger. "I was Sukie's age when he became my only parent. I think my earliest memories are of him holding me that way. I loved him so much. But being away so long… that hurt."

"Well," Jackie told her. "He's here now, and it seems like he's more than making up for being gone. You shouldn't feel bad about him."

"Mum," Rose said. "You don't even like him."

"I don't like him being with you," Jackie answered her. "But his own family… that's another matter. He's still a nine hundred and fifty year old alien. It's too weird."

"I'm an alien, too, Jackie," Susan replied quietly. "I was born on Gallifrey."

"Yes, I know But… Oh, I don't know."

"I do," Rose said. She had seen The Doctor appear at the door. She stood and went to him.

"I have persuaded them to go ahead - despite this being a little unorthodox. They're getting ready to start. So…" He said nothing more. He simply pulled her closer in his arms and held her for a long time. Susan came to them and he hugged her too, then he went with the doctors and they were left to wait.

It was easier, Rose thought, last time when she was with him through the operation. She wished she could be with him now. But this operation was done under a local anaesthetic and his peculiar physiology was less affected by it. He didn't need her this time. All she could do was wait.

Funnily enough, it was her mum who held them all together. She went to the vending machines and got coffee for them and soft drinks and chocolate for the boys. She took care of the baby while Susan was too distracted to think of anything but whether the two men dearest to her in the world were all right. Her ambivalent opinions about The Doctor she kept to herself. Rose suspected that even her mum was worrying about him, and not just because he was the only person who could get them both home again.

At last, they were called. Rose and Susan were both nervous. But when they went through to the recovery room they found The Doctor was sitting in a chair dressed in his usual clothes, looking relaxed and healthy. David was sitting up in the bed. He looked ill, but not deathly so. Both found themselves being hugged moments later.

"Doctor…" One of the hospital doctors came up to him as Rose finally released him from her embrace. "I wonder if YOU could explain these test results. They are beyond us."

The Doctor took the printed pages from him and read through them in his usual super-fast style, his pupils dilating rapidly.

"It's quite simple. David's DNA has been fused with mine. He has taken on some of the characteristics of my race. Specifically, resistance to illness - His immune system is not only repaired but better than it was. He will, I think, have the same lifespan as a non-regenerative Gallifreyan."

"I have?" David was astonished. "But…" He clutched his wife's hand and looked at her grandfather. "But…"

"Yes, I know," The Doctor said. "It's something you've wanted ever since you realised that your wife and children had a potential life span ten times greater than yours. You've hated the idea of dying so long before any of them."

"Yes," David said. "But…"

"Did you know that would happen?" Susan asked him.

"I thought it might. But I wasn't sure." He looked at the notes again. "Yes. It's definite. The DNA has been changed."

"I'm… like you?" David was still virtually lost for words.

"Like Susan. She doesn't have the regeneration capability. Neither will you. But in some ways, that's not a bad thing. One good life lived well is as good as 12 wasted ones. It's up to you what you do with it."

"This is incredible," the doctor said. "If we could replicate these results… The benefits to mankind…"

The Doctor looked at him with a strange glitter in his eyes. He dropped the report in a waste paper bin and with a flick of the sonic screwdriver that he pulled from his pocket it burst into flames.

"You will find when you check your computers, that all the details of David's admittance to the hospital and his operation have been corrupted. If I have to, I can do the same to your memory of the past few hours. But I'd rather have your word that you won't follow this up. I am nobody's test subject. Nor is David, or any of his family. Mankind can work its own benefits out." And he turned one of his hardest stares on the doctor who seemed to flinch back from him. "David, that paper said you're perfectly well to leave the hospital. I think we'll ALL leave now." Susan was already helping him into his clothes. Rose went back to the waiting room to alert Jackie and the boys that they were leaving. Minutes later they were all in the TARDIS and the Doctor was setting the co-ordinates for David and Susan's home.