"New York, 1943," the Doctor announced, stepping out of the TARDIS and shoving his hands in his coat pockets. He sounded pleased as punch, as he always did whenever he managed to get to the right place and time – and often when he didn't, Donna thought fondly, following him out. "America's been in the - "

"How did you make the box appear like that?" a young, demanding, aristocratic voice interrupted. It wasn't quite an English accent – but it positively exuded wealth and money. Donna looked down in surprise to see a boy, dressed in a sharp suit, staring at them and the TARDIS accusingly.

"Hang on," she said, looking between the boy and the TARDIS. "How did you catch that?"

"That's a very good question," the Doctor said, looking quite surprised. He whipped out his geeky glasses – Donna knew he didn't need them, and one of these days she might even get him to admit it – and crouched down, peering at the boy like he was some fascinating specimen. Donna rolled her eyes, well remembering how irritating it was to be treated like that. She kicked his ankle, eliciting an, "Oi!"

A proper, matronly woman came rushing up, looking quite frazzled; her hair was still black, without a hint of grey, but she had far more lines on her face than one might expect. Then again, Donna supposed, this was 1943 – right in the middle of World War II. "Charles," the woman scolded the boy, trying to take his hand, "You mustn't wander off like that! You know – "

"Oh, do leave off, Nanny," Charles said crossly. Donna felt a chill go down her spine as Nanny's eyes went blank. The woman wandered off without another word.

"Now, that's not very nice," the Doctor said, but he was grinning fit to burst – and he'd taken off the glasses, too. "Charles – that wouldn't happen to be Charles Xavier, would it?"

"I didn't mean to," Charles said, sounding stricken as he stared after Nanny. A moment later, though, he turned to the Doctor again, his face showing both suspicion and wonder. "How do you know my name?" The way he demanded an answer should have sounded petulant, coming from a boy his age, but it didn't, Donna thought with surprise; for all his youth there was power behind those words.

"Hey, that was rude!" the Doctor protested, jumping to his feet. He turned to Donna. "That was rude! Him, not me!" He turned back to Charles. "You can't just go around poking in everybody's heads and compelling them obey you, you know, it's no way to get on in life and – " he broke off, searching Charles's face intently, then went back to grinning like a maniac. "Oh, this is good! You have only the faintest idea, don't you? This is brilliant!"

"Oi, Space-boy," Donna broke in impatiently, before he could really gather steam. Best to head him off early, she'd learned, or he could go on for hours about how fantastic something was without explaining anything about what it was. Or, in this case, who. "A bit of context?"

"Yes, of course," the Doctor beamed. "Charles Xavier, I'm the Doctor, and this is Donna Noble. Remember the Mutant Rights movement?" he asked her, and after a moment she nodded vaguely. She didn't really know anything about a movement, but there had been a march that had held up traffic for three hours one Saturday, and the word MUTANT was all over the signs, although she wasn't really sure what it had been about. But there had been Joy, too, Mrs. Bernstein's secretary at H.C. Clements, and everybody had said she'd gotten fired over being a mutant, so Donna supposed that if something like that was going on, then there was probably a movement about it somewhere. "You're looking at the brain of it, Donna – the most powerful human telepath ever born." He paused for a moment, and then made a face. "Well, second-most powerful - but not by much! Charlie here could out-do an Ood any day, he could – seeing through a perception filter is easy-peasy stuff for you, isn't it?" This last was directed at Charles, fondly, but Donna knew the Doctor well enough by now to see the hint of underlying wariness.

"Mutant rights," Charles said slowly, staring very intently at Donna. "You think I'm a – a mutant?" The wonder was overtaking suspicion in his voice. "There are – you mean that there are others like me?" For some reason, Donna thought strongly of Joy again, remembering the way her hair seemed to change colour multiple times every day – which would be a bloody awful mutation to lose your job over, Donna thought –

"Ey! No rummaging about in her brain, either!" the Doctor interrupted, and suddenly Donna could think about something other than Joy's hair.

"I'm not meaning to," Charles insisted defensively.

Dragging a kid along with them really wasn't doing much for their whole 'Not Married' routine, Donna decided, as the platapus-person in front of her nattered on about, "Oooh, how sweet of you to bring your son along, we don't really get many humans all the way out here – "

"Not our son," the Doctor said absentmindedly, before Donna could slap a hand over his mouth to stop him from talking. Hadn't he learned his lesson when the natives of Lawrence IV had decided last week that Charles had been kidnapped?

"Kid brother," Donna said hastily, adding on, "His," because with the way Charles could geek out over things she sometimes wondered if he wasn't.

"Right, kid brother," the Doctor agreed cheerfully. "He loves tagging along, he just – " The ends of his long coat swirled around him as he turned back, then forward again, then back again. Donna frowned and looked around herself. Charles had disappeared. "Doors, Charlie," the Doctor said, sounding exasperated, and the boy reappeared next to Donna, looking chagrined. She managed not to jump this time. Apparently, Charles also had been anticipating another child-custody battle. At least he hadn't accidentally frozen everybody this time.

"Oh, I'm sorry, I shouldn't have just assumed you were full human," the platapus said sheepishly. "I didn't realize you had some Invisible DNA in you. Though you do look quite human, I must say, I thought everyone from the Disappearing Planets had beaks like us - "

"Year 2087," the Doctor cheerfully declared, while Donna and Charles stared about in wonder. It looked more like an alien planet than it looked like Earth 2007 – and Charles had found even the early twenty-first century fascinating. "The Mutant Pride Day Parade, founded after – a rather important anniversary." Donna barely caught the hesitation; Charles didn't notice at all, she thought. "Mutants make up about thirty percent of the total population, with a good four in five being very visible, though most can turn it off if they want – colourful, aren't they?" the Doctor said, grinning like a kid in a candy shop. They'd arrived in the middle of a parade. At first, Donna had thought it was another march like the one that she'd run across back when life was boring – but this was more than that. This was also a celebration.

Winged humans flew overhead – all kinds of wings, she marvelled; bird-like and insect-like and even a few that looked reptilian – and furry, scaly, or just plain weird looking people walked down the street, side-by-side with people who looked like plain old humans but then one would occasionally shoot fireworks into the air, or another would flare gold all over and rise up to join the flyers. There were old people and young people, men and women, all sorts of different races and nationalities (though, with some of the more visible mutations, it was sort of hard to tell with only a glance), but what struck Donna was how happy they all looked.

"See?" the Doctor said, smiling down at Charles. "I told you that you weren't alone."

"They're like me," Charles breathed, his face lit up in wonder. "I can hear them."

"Mind the doors," the Doctor reminded him, but he was grinning, looking out over the crowd, too. "Come on, let's join in!" And he grabbed their hands and pulled them into the march. "There aren't just mutants in this bunch," he told Charles. "Try looking at them from overhead, like I showed you."

"I can see them!" Charles said excitedly. "They look – they look red, and the others look white. There are non-mutants here, too!"

A young man walking near them grinned down at him. "Course we're here," the young man declared, throwing his arm around a woman with silver skin and kissing her on the cheek. "We're all people, aren't we?"

It was New Year's Day, the first day of the third millennium, in fact; they came to celebrate it in London. It was Donna's request; her first try at the millennial New Year had been rather poor, and she'd wanted another go at it. She hadn't expected to end up in a chip shop, watching Charles appear to change shapes as he practised projecting something other than invisibility. The Doctor had taken one look at the shop and gone all funny, before going off to sulk in the TARDIS.

"Do you think he's all right?" the young, Japanese-looking woman sitting across from Donna asked in Charles' voice. Her eyes were flickering, changing between a natural-looking black and Charles' own blue.

"He'll be fine," Donna sighed, but she knew she wasn't fooling anybody, let alone a telepath.

"You're lying," Charles said, flickering back to himself. He sounded delighted. "I couldn't tell – I mean, not automatically. I didn't feel anything from you – I think I was projecting too much." Then he frowned. "I can never tell why he's unhappy. He always shuts the door in my face when I look at him. And I wouldn't want to try battering it down, that would be wrong."

"You've got that right," Donna said, pointing a chip at him. Most of the time Charles was a good kid, but now and then he said something that was just plain freaky. "You shouldn't be peeking in at all, you know that. I thought he'd taught you to how to avoid doing that."

"He did," Charles said, fidgeting guiltily. "But it feels like – I don't know. Like keeping my eyes closed all the time." He looked so earnest that she felt a wave of sympathy for him despite the horrible invasion of privacy, and she didn't know what to say.

"Have some more chips," she offered instead, pushing the carton closer to him.

They'd gotten fish 'n' chips, with the fish coming wrapped in old newspapers, the grease turning the paper translucent, the ink standing out sharp against it. Charles fiddled with the paper left-over from his, unfolding it against the table. Then he went very still, staring at it. "What is it?" Donna asked. Since he'd finally managed to get control of the doors in his own mind, at least, Charles had been harder to read. His face was still as expressive as ever, but he no longer projected his emotions to everybody nearby - even if he had just admitted to still eavesdropping on them in return.

He turned the paper around so she could read it properly. INTERNATIONAL MUTANT TERRORIST MAGNETO ESCAPES CUSTODY, the headline screamed, along with a picture of the man in question. She had to snort a bit – although she'd seem some pretty weird get-ups on alien worlds, there was just no excuse for a man his age and in this time to be wearing a helmet and a cape like that. When she looked back at Charles, though, and saw his expression, she regretted it.

"Oh, sweetheart, mutants are just people too," she sighed, reaching over and giving his hand a squeeze. "And some people are bad. Just because he is, doesn't mean all mutants are."

"The article says his name is Erik Lensherr," Charles said, sounding lost and confused and hurt.

"Erik – " That name was familiar, and recently so. Donna squinted, trying to remember where she'd heard it before – from one of the Doctor's endless babbles, it seemed, going on about – oh. "Is that - your Erik?" she asked tentatively.

"I don't know," Charles said, troubled. "He can't be, can he? My Erik isn't – won't, I mean – be evil. I'm not evil." He sounded very matter-of-fact about this last part. "So, he can't be."

"Oh," said the Doctor, staring at the newspaper.

Charles' eyes narrowed. "He is my Erik," he said flatly. "How can he be my Erik?"

The Doctor looked away; Donna tried to catch his gaze but he avoided her, too. "Not all friends stay beside you always," he said, and a chill ran down Donna's spine as she recalled where she'd heard that tone before – when he'd been speaking of Rose. When he said that he'd 'lost' her. But Rose was alive, and certainly not an evil terrorist.

"But you said we'd be best friends!" Charles cried, the newspaper crumpling in his grasp. "Why did you lie?"

"I didn't. You will be," the Doctor said, quiet and old. "Nothing lasts forever."

"Why? Why would I have an evil best friend? Am I supposed to turn evil? I won't," he insisted, tears rolling down his cheeks. "I won't be a murderer, I won't be a terrorist, I won't kill people – "

Donna broke in, gently taking the newspaper from his grasp. "Of course you won't," she said, kneeling down and putting an arm around his shoulders. He was shaking. "You never would – "

"How would you know?" Charles accused her angrily, pulling away from her. "You didn't know who Erik is – you didn't know who I am – " he turned back to the Doctor, his hands turning into fists. " – only he knew, and what are you hiding from me?"

He raised both hands to the sides of his head, fingers pressing at his temples like he had a terrible headache. But it was the Doctor who gasped in pain, who stumbled back against the TARDIS' console, who choked out, "No – don't!"

"Charles, stop," Donna begged him, "Please!"

Charles didn't listen to her. He didn't look much like a boy anymore; the expression on his face was full of anger and knowing. Two months ago she'd have been able to feel that anger. He'd have been pouring it out to the entire room. Now he had focus, deadly and terrifying, and the only thing she felt was her own fear. "You've done this before. I can see it. I can see him. I won't be like you, Doctor – I won't let you let me make your mistakes! I won't!" Charles shouted, his voice echoing off of the room. "You'll show me what happens, and I'll stop it!"

The Doctor gasped again, and gritted out, "You can't. No one can. I'm sorry." There was a terrible, malevolent power in his voice, and Charles' eyes widened as the Last of the Time Lords spoke.

They were both silent, Donna staring at them desperately, for one long and aching moment, and then a truly awful expression flickered over Charles' face. It was despair – despair so deep that it hurt to see it on someone so young.

"I'm so sorry," the Doctor said into the silence. "You weren't meant to see that." He reached out with one hand, stepping forward, but Charles backed away, side-stepping toward the ramp.

"Stay away," he told the Doctor flatly, and the Doctor nodded, retreating to the other side of the console, head bowed. "I want to go home," Charles said, very softly, tears tracing down his cheeks, but he wasn't sobbing. The rage had disappeared; he was as still as a statue. "Take me back. Now."

"Right," said the Doctor, equally subdued. "Westchester, then – " He flipped a lever and the TARDIS shuddered, sending its occupants reaching for the nearest hand-hold. "Here we are."

Charles marched down the ramp, silent and solemn. Her heart breaking – in a way that she'd never felt before she'd met the Doctor, she knew – Donna reached after him. "Charlie," she said, her voice trembling, but that was as far as she got before he whirled on her.

"Leave me alone," he said, still very quiet, and she felt something freeze in her brain. Then she blinked, and it – and Charles – was gone, vanished into thin air.

"Doctor!" she protested – somehow he'd gotten from one side of the console to the other in the blink of an eye; Charles must have frozen her, she realized, with a touch of indignation. "We can't just drop him like – "

"Can't I?" the Doctor said coolly, cutting her off. He slammed down the lever, sending them back into the Vortex.

Charles curled up in his bed – it was neatly made, though the room itself was dusty enough to make him sneeze – and watched the TARDIS disappear with its screeching and groaning. He wiped tears from his face impatiently, struggling not to start crying all over again. Focus, he thought, closing himself deep in his mind and slamming all the doors to the outside shut.

But he couldn't escape the future, couldn't escape the way the Doctor had looked like he wanted to cry himself, when his thoughts looped in endless circles of, "I'm so sorry. I'm so very, very sorry." He couldn't forget the feeling of utter certainty that he'd felt in every room and every hallway of the alien's mind, the knowledge of doom and despair, the picture of himself, crippled and alone long before he'd even reached Donna's age. His best friend – oh, what a cruel joke that was. They would be friends only for a short while, and then Erik would turn, and they would spend all their remaining decades as enemies, growing old and bitter. Alone.

He would fail to keep him, and there was nothing he could do about it, because Erik was a Fixed Point and not even the Doctor could change that.

"I'll fix it," he whispered to the dark, feeling tears well up again.

"I'm so sorry."

There was nothing he could do, and it felt like he was being crushed beneath a mountain, and he couldn't breathe, he couldn't – he couldn't –

Charles woke, yawning, to the sunlight streaming through his window. Nanny must have forgotten to draw the curtains, he supposed. Or maybe he had, he thought, as he realized that he'd slept in his clothes – had he meant to sneak out last night? If he had, he'd fallen asleep before he could do so. But she wasn't here to wake him, either. Perhaps she was ill; she'd been acting very strange, lately.

He changed into something less wrinkled and made his way downstairs and to the kitchen; his stomach was growling. There were sounds coming from inside; Cook, of course, would have long since woken up. He entered, feeling strangely reassured by the sight of her large form and stained apron.

She turned, caught sight of him, and shrieked, dropping the pan that she was holding. It fell to the floor with a crash. "Master Charles! Oh, my –Master Charles, where have you been – " Footsteps pounded upstairs; someone was coming at a run, no doubt alarmed by her scream.

He frowned, wondering what she was talking about – but he could find out, couldn't he? He checked, not quite sure how he knew how to do so, but not really caring how he knew, either. She thought that he'd been missing for... missing for weeks? That was preposterous. Something deep inside him found it frightening. He didn't want to be asked about it, didn't want to think about it.

"I've been here, of course," he said firmly, and as soon as he said it he knew it was true.

Cook's eyes went glassy, and she got that same strange look on her face that Nanny had been wearing more and more often lately. "Of course," she said blankly, and then smiled kindly. "You slept in a bit late, didn't you, Master Charles? Well, you know you're always welcome to come have breakfast in the kitchen. Would you like a spot of egg and toast, then?"