Clara Oswald had the unenviable task of supervising Thursday evening detention. Eight of the usual suspects were scattered among the thirty desks in the fourth year form room writing essays with a randomly chosen title - a rusty bed spring.

She had no illusions about any of them taking the opportunity to write something imaginative and worthwhile. She wasn't even sure Chad Inglesby could even write. Most of the others were writing on every other line to use up the minimum five sides of paper more easily.

As long as they were quiet, she didn't really care. She would be as glad as the students when the time was up and they could all go home.

Suddenly there was a stirring, surprised murmurings, and chairs scraped back. Anita Robbins squealed, leapt up from her back seat and ran for the door.

"Sit down," Clara told her. Then as Anita bolted down the corridor she glanced around at the rest of the class and saw the reason for their concern.

There was a ghost in the classroom.

At least it looked like a ghost. It was a girl - a teenager - in a school uniform that belonged to a past decade. She looked lost and frightened.

She was translucent. Clara could see the world map on the back wall through her.

The translucent girl looked straight at Clara and mouthed something silently.

She wobbled and then became a little less translucent, fading in like an old analogue radio station.

She tried to speak again. This time Clara thought she heard the words "help me" coming to her from a long way off and very close at the same time.

"Everyone grab your bags and go," she said to her petrified but at the same time curious students. "Detention is over. Go home."

Some of them stuffed pens, books and half done essays in their bags and ran for it, either out of fear of the apparition or joy at being let off detention. A few took their time, obviously curious about what was happening.

"Go on, beat it," she told them. The last straggler left the door swinging. She closed it and turned to the ghost girl.

She wasn't really ghostly now. She was quite solid and perfectly ordinary except for two things.

The uniform that was so out of date was one thing.

And the fact that Clara recognized her.

"This is the fourth year form room?" the mystery girl asked. "It looks right, except that Miss Anderson who teaches geography always had a really old map of the world with the Empire shaded in red up there where that one is. She doesn’t like countries going independent and leaving the Commonwealth.”

"We wouldn't be allowed that map now,” Clara answered. “It would offend students who came from the former Empire countries." The girl laughed as if she understood the joke about political correctness. "It's Susan, isn't it? You were Susan Foreman when you went to this school, but obviously that’s not your real name.”

She looked suddenly scared – like a frightened pony getting ready to bolt. Her dark eyes were wide and her elfin face even paler than before.

"It’s all right," Clara assured her. "I know who you are. He told me. The Doctor... your grandfather. I know him. He's a friend of mine. "

“He is?” Susan was surprised by the idea. Clara wasn't entirely surprised by her surprise. The Doctor was not an easy friend to have. Susan obviously knew that, too.

"Come and sit down." Clara gently brought her to the front row of desks and eased her into a chair. She pulled a second chair around next to her.

"I recognised you from a picture he once showed me. He was acting a bit daft about me getting a job in this school, and eventually he explained why. I know the name you used from the old school registers. I looked you up out of curiosity.”

Susan didn’t seem to know what to say about that. She just looked around the classroom noting the familiar and unfamiliar about the school she attended in the nineteen-sixties.

“It wasn't just sentimentality… him not wanting me to work here. He said that my being here after travelling in the TARDIS… and you being a student back then… might trigger a temporal rift. I told him he was just being a dog in the manger about me getting my first teaching job, but...."

She smiled in what she hoped was an apologetic tone.

"He was right. It is my fault. Me, full of TARDIS background energy. I must have dragged you here through time."

"It’s all right," Susan assured her. "You really couldn't have known this would happen. Is he.... grandfather... is he well?"

"Fit as a fiddle," Clara answered. "He's regenerated, of course. Lots of times. I was there when it happened last time. He 's grumpy and Scottish, now."

"Scottish?" Susan laughed at the very idea. Again, grumpy was no surprise to her.

"I need to get home to nineteen-sixty-three,” she said after a long silence. “He... grandfather... back there... will be really worried. He worries about me any time I'm late. He thinks I might get into trouble."

Clara suspected she didn’t mean the kind of trouble most girls her age got into after school.

"I suppose you don't know how to do that?" Clara asked. "Get back to your time. You don't know any clever Time Lord stuff to reverse what happened?"

"No," Susan answered ruefully. "I'm only fifteen. Training to be a Time Lord doesn't even begin till twenty. Grandfather has taught me a lot, but not how to travel in time without a TARDIS."

“Then I think we need him," Clara decided. She took out her mobile phone. Susan looked at it curiously.

"He never lets me have any alien devices in case anyone gets suspicious. He's worried about the government wanting to use us as weapons in the Cold War."

"This isn't alien," Clara assured her. "It’s a Nokia. He souped it up to call him on the other side of the galaxy without it costing a fortune but it is made in Finland."

She pressed the speed dial button that rang a number across time and space.

She got the answering machine.

"Hello, it’s me, but I'm out somewhere saving a planet - probably Earth. If it is important, leave your message after the tone. If it isn't don't waste a resource like free universal roaming on trivialities."

"Typical," Clara murmured. She waited for the tone. "Is this important enough?"

She asked her question then quickly passed the phone to Susan who looked at it dubiously before speaking into the receiver.

"Grandfather, please help me."

She gave it straight back to Clara who had a little more to say.

"We'll be at Costa around the corner from the school," she said before closing the call. "Come on, Susan. School is over for today."

Susan didn't know what Costa was until they reached the coffee shop where Clara bought two long macchiatos because she thought somebody who had been dragged through time from nineteen-sixty-three deserved a really nice coffee.

"This was a dress shop in my time," Susan commented as they both looked for an opening into a conversation. "A lot of things have changed."

She looked out through the café window at the traffic inching its way through the evening congestion. She looked at the collection of stickers on the window indicating that several different credit and debit cards were accepted and one offering free wi fi. These were just a few of the differences about this world from her own, even if it was still East London.

"Yes, they have," Clara agreed. "I think you would be amazed."

"The air is cleaner. But it is much noisier. The cars...."

"I think the individual cars are quieter," Clara admitted. "But there are more of them."

"Yes, I suppose that explains it." Susan again looked around the cafe and glanced idly at the menu. "Britain has the decimal system, now."

"Since nineteen-seventy-one."

"I always thought it made more sense than shillings and sixpences and all of that."

There was some more small talk before Susan felt safe to ask a more pressing question about what had changed.

"Have you been his friend for long?"

"About three years, give or take, not counting weekends that took a month on another planet. Most of it has been interesting. Some of it fun. A lot of it terrifying.”

“That sounds like life with grandfather,” Susan admitted with a wry smile.

“He was there for me when I needed him more than I ever needed anyone,” Clara added. She didn’t expand on that, but Susan seemed to understand.

“He can be… difficult… but he can also be very understanding and kind.”

“Yes.”

“He will be so worried,” Susan added. This was her most pressing concern. Clara wondered how somebody who lived in the TARDIS could be ‘grounded’ for being late home.

“Don’t worry. When he… my Doctor… gets here, he’ll sort everything out.”

“I expect so.”

Susan didn’t quite look convinced.

“You know he will. It might be a long time since the two of you lived in London… I’m not even sure exactly how long… but you know you can depend on him. He’ll think of something.”

“If he gets here. What if….”

“Don’t let ‘what ifs’ get you down. Apart from anything else HE won’t let you give in to worries like that. He is really down on anyone giving in to pessimism or self-pity. Anyone except himself, anyway. When HE is worried about something he can really moan, but nobody else is allowed.”

Susan laughed again.

“That sounds like him. He does have so much to worry about, though. I suppose I don’t help. I wanted so much to live an ordinary life, and sometimes I don’t get it right. I’ve made lots of mistakes at school.”

Clara nodded. She had looked at those old school records very thoroughly. Every teacher had made some kind of note at some point. Susan was the girl who didn’t know about pounds, shillings and pence, yet could do calculus in her head. She was the girl who didn’t know the current prime minister or when Queen Elizabeth II came to the throne, but could write a thousand word essay about the French revolution in her lunch break, without any text books for reference. She was appalling at geography and didn’t even seem to know what the British Empire was, even with maps to help. She was brilliant at languages, speaking French and Spanish like a native, disinterested in science, which seemed to bore her. She took no part in sports….

Most disturbing of all, she seemed to have no friends of any kind, and took no part in any extra-curricular activity.

“Grandfather always tells me to be careful. If anyone finds out the truth….”

Clara wondered why either of them worried so much. Coal Hill’s teachers seemed to have summed her up between them as an unusual student, but it was unlikely that any of them would have come close to guessing that she was an alien from a far off world where the aspirations of the British Empire would seem parochial and calculus was a game for infants.

Then again, he had never actually explained why they left Earth in the nineteen-sixties. Perhaps somebody did begin to suspect.

Clara was going to ask a few more questions but Susan had thought of something else.

“I’m not with him in your time?” she noted. “Where am I?”

Clara didn’t answer straight away. Susan groaned and beat her forehead with her fist.

"That was very stupid. I should never have asked that question of you. It is knowledge of the future. Grandfather would be very angry with me for asking. You were right not to tell me."

"It's not that," Clara assured her. “I just don’t know. He never said why the two of you went your separate ways. But… I don’t think anything bad happened. He doesn’t talk about the past very much, because he’s a stubborn, awkward old man who won’t answer a straight question about anything, but I’m sure everything was all right.”

"I always thought I would ..." Susan began. Then whatever she meant to say died on her lips. Her face froze and her wide eyes stared at the cafe door. “Grandfather!”

Clara turned and recognised The Doctor. She wondered how Susan had known him. He looked completely different now than when he was her grandfather.

The Doctor took five paces towards them and stopped. Susan stood and took one step towards him before her courage failed. For almost half a minute they just stared at each other.

"Oh, for heaven's sake!" Clara rose and gently but firmly pushed Susan towards The Doctor. "You’re family. You love each other. Hug, now, and no excuses."

The Doctor reached out and embraced his granddaughter in a hug to end all hugs. Other coffee drinkers turned and looked at the touching reunion even if none of them realised how long this one had taken.

There were tears - from them both. It was Clara who made them both stop crying and talk. She ordered more coffee while grandfather and granddaughter dried their eyes, then they got down to discussing the immediate problem.

"I thought you could just take Susan back to her proper time in the TARDIS," Clara said when The Doctor talked about how complicated it all was.

"No, I can't," he answered. "I can't risk my TARDIS being in the same time zone as itself from back then. I can't risk me being there with myself from then for the same reason."

"The reason being..." Clara demanded.

"The TARDIS and I were both old and some of our parts were worn. Going there might seriously damage her or give me a fatal hearts attack - causing in turn a massive paradox if I'm taken out of existence at that stage in my lives."

"Ok, that's a no, then," Clara concluded. "So what other options are there?"

“I can make a device that will open the rift up again, so that Susan can return. It will take me a few hours. Three… four at the most. Five or six….”

“What will I do in the meantime?” Susan asked. “Can I stay with you, Grandfather?”

“No,” The Doctor replied, too quickly, too gruffly. Susan was startled and a little dismayed by such a reaction. Clara glared at him and was about to remark on his rudeness when he clearly realised his mistake for himself. “No, Susan. I’m sorry, it just isn’t a good idea. There would be too much risk… I mean….”

He took out his sonic screwdriver and scanned her. Susan’s expression changed to one of fear. “It is perfectly harmless background rift energy,” he assured her. “But it would be better if you weren’t near the TARDIS. I mean harmless to people, not to time machines.”

“I see,” Susan replied in a small voice.

“Come home with me,” Clara told her. “I’ll get some pizza on the way and we’ll watch a DVD. I don’t think it will cause time to unravel if you see a Zac Efron film in twenty-fifteen before heading back to the era of… whoever was the film heartthrob in the sixties.”

“Cliff Richard,” The Doctor remarked dryly. “For her, anyway. Yes, that’s the best idea. I’ll come for you both when I’m ready.”

Clara stood up and reached out her hand to Susan. The two of them walked out of the café, leaving The Doctor still sitting at the table.

He waited and watched the two of them walk on down the road. None of the other customers were looking his way now that the little family drama was over. Nobody noticed a stray tear on his care-worn face or the quick movement that brushed it away.

The truth... that he couldn't share even with Clara... was that it would have been too painful to have Susan with him in the TARDIS. This short time here in the neutral ground of the cafe was hard enough. The temptation to tell her things he had never told her at the right time was too great. Or worse, to say things that might give away too much about their future - the future from her point of view, not his distant past.

He wasn't emotionally ready to spend that much time with her.

There were whole minutes at a time when Susan forgot to be anxious about her predicament. She forgot everything except pizza and the splendour of watching a film on Clara's wide screen HD television.

"Surely there are more spectacular televisions on Gallifrey?" Clara queried when the film was over and they sat drinking coffee and watching the DVD extras. "The Time Lords are so clever. They must have surround-tv or something.

Susan shook her head.

"We just had the public service broadcast. It was mostly information - proclamations from the High Council and exchange prices. I never saw television for entertainment until I came to Earth. But nineteen-sixties television is nothing like this."

"No. We've come a long way with our entertainment technology. I'm not sure the quality of programmes matches the equipment sometimes."

"Well, I think it is wonderful," Susan decided. "I wish we could have something like this in the TARDIS."

"Susan, you mustn't mention this or anything about what happened here to your grandfather... the version of him back there in the nineteen-sixties. Not even about the television. I'm sure my version of him could explain why better than I can, but you just can't."

"I know," Susan admitted. "Everything is about secrets. My real identity is a secret at school. This is a secret from grandfather. We're both a secret from the government. Grandfather has more secrets of his own that he can't even tell me. Sometimes I am so tired of secrets."

"I know the feeling," Clara assured her. "I tried keeping my friendship with The Doctor secret and it nearly ruined every other part of my life... even the chance to sit and watch television quietly by myself."

"I think you really DO understand," Susan told her. "If only we didn't live in different decades. We could be friends. It would be so much easier if we could share our frustrations over coffee."

"If we were in the same time I'd be your teacher not your friend," Clara pointed out, but even so, I think you're right. It would be nice to share the burden... as well as the joys of knowing The Doctor. There ARE some of them, after all."

"Yes," Susan admitted. "And at least we have had this lovely evening."

There was still time enough for more coffee and more girl chat before the rhythmic knock at the door that Clara recognised as The Doctor's arrival. Susan stood nervously as Clara let him in. The cosy evening was well and truly over.

"I've done it," he announced. "We need to go back to the school, of course. The rift energy signature needs to be exact."

Clara glanced meaningfully at the clock. It was after midnight.

"We need to break into the school. You had better have brought your burglary kit."

He held up his sonic screwdriver Clara admitted that it would do.

The Doctor took Susan's hand as they headed for Clara's car. He sat next to her in the back seat with his arm around her shoulders. Neither spoke much, but Clara guessed that some making up for lost time was going on. She kept her eyes on the road and stayed out of it.

The break-in to Coal Hill school was accomplished without any undue problems. Clara opened the geography classroom - also known as fourth year form room - and stepped in, noting how odd it all looked in the dark, with only a few street lights outside illuminating the desks closest to the window.

“Susan, I want you to take this," The Doctor said, giving her a small glowing crystal on a piece of silver chain. She hung it around her neck as if it was a precious piece of jewellery that she would treasure forever.

Perhaps she would at that. It came from HIM, after all.

"It's all very easy," The Doctor told her. "Hold the crystal and walk backwards the way you came. The spark of artron energy in the crystal will boost the natural energy inside you and pull you home. You will go back to exactly where and when you slipped through. Afterwards the crystal will seal the rift and then the energy will dissipate. This won't happen again."

"A one way trip," Clara noted.

"Yes."

"That's a pity," Susan remarked. "I almost thought the crystal would let me come to see Clara when I wanted."

"That can't happen, for so many reasons," The Doctor told her.

Susan nodded silently, accepting his word about that. They hugged once, then Susan walked backwards away from him, towards the world map on the wall at the back of the classroom.

She bumped into the map on the wall and looked at The Doctor and Clara anxiously.

"Oh dear," The Doctor said in understated tones. "Something is wrong.”

“No kidding,” Clara remarked. Susan came back to them, her face a silent picture of disappointment.

“It’s YOU,” The Doctor told Clara.

“What do you mean, it’s me?” she replied indignantly.

“You’ve got artron energy in you, too, from the TARDIS. You’re pulling her back.”

“Why couldn’t it be you?” Clara asked.

“I used up all my artron energy the last time I regenerated. It’s you.”

“So do you want me to leave?”

“No,” The Doctor answered. “That wouldn’t work. I think you should go with her.”

“Go where?”

“To nineteen sixty-three?” Susan queried.

“You said it was a one way trip. I’m not getting stranded in the sixties. I’d be middle aged by the time Thatcher became prime minister. Uggh.”

“Don’t worry, that won’t happen. I’ll come and get you. Susan, what was the date when you came through the rift?”

“November the fifth, nineteen-sixty-three,” she answered. “Bonfire night. I was the only one not going to the recreation ground for it. I really don’t like that sort of thing, and besides, grandfather… I mean… you… wanted me home on time.”

“November the fifth is fine,” The Doctor said. “Clara, I will need you to stay for three weeks. Here.” He reached into his coat pocket and gave her a roll of money. She looked at it and calculated that there was about a hundred pounds in very old five pound notes. “Stay in a hotel. Meet me on November the thirtieth, four o’clock, outside the Shoreditch library.”

“Why three weeks?” Clara asked. “What difference does that make?”

“It makes a difference. Susan, you and Clara should avoid meeting during that time. I know you have liked each other’s company tonight, and there are lots of reasons why you could be friends. But it can’t happen. Both of you trust me about that.”

Both of them looked disappointed, but they nodded and promised to do their best.

“All right, let’s try again. Hold hands, both of you, and walk backwards.”

The Doctor stood as far away as possible, beside the teacher’s desk. Clara and Susan faced him and held hands. They walked back, slowly, towards the far end of the darkened classroom.

“Oh!” Susan cried out in alarm. It was still dark, but now they couldn’t see The Doctor. Clara turned and looked at a world map on the wall. It showed the British Empire nations coloured in a faded, pinkish red.

“We did it,” she said.

“We’d better get out of here, then,” Susan pointed out. “There is a caretaker who checks all the rooms before locking up.”

It was only a little after four o’clock, but it was November and foggy out. Clara and Susan slipped out through the main door and across the playground. The street lamps gave enough hazy light for Susan to find her way to the junkyard in a side street where she lived. Clara walked with her, despite her insistence that she could manage. She felt that her duty of care extended that far.

“You’ll be all right, now. I think I can find my way to the main road. I’m not sure where I’ll find a hotel, though.”

"There's a hotel for young Christian women on East Road," Susan told her. "You'll be able to get in there. Madam D'Astine, our French mistress, is a long term boarder."

"That sounds respectable enough," Clara admitted. "You'd better get on in, now. All the best to you."

They hugged briefly, then Susan slipped in through the gate with the name I.M Foreman split across the two halves. Clara heard her call out to her grandfather and a gruff voice answered, admonishing her for being late. There was a sound of a door opening and closing and then silence. Clara turned and walked away in the dark.

Three weeks later, she found the Shoreditch public library and waited. She was more than a little bit relieved when the TARDIS materialised and her Doctor emerged from it with a smile on his lips.

Clara hugged him whether he liked it or not.

"I have missed you, modern underarm deodorants and big colour televisions in that order," she said. "I saw the assassination of John F. Kennedy on the little black and white in the hotel lounge. I was actually here for it. When people go on about where they were when it happened I can say I was in a hotel in Shoreditch." She shook her head. "Well, maybe not."

"I remember it well," The Doctor admitted.

“I’m only surprised you weren’t hanging about the grassy knoll,” Clara told him. “You and Susan disappeared that same week. Along with two teachers. It made a small column in the local paper."

"Yes."

"That was when you left Earth and went travelling again. You knew it would be safe to come and get me after that. You and the TARDIS were gone from this time."

"Indeed."

"Ok. Now can you get me back to my flat on the day I left it? I don't want pizza crusts going mouldy while you get me lost in the Draconian Triangle."

The Doctor grinned. Clara wasn't sure whether that was reassuring or not, but she stepped into the TARDIS ready for anything to happen.