"Wait, what?"
"Amy, you heard me the first time. Now, I need to-"
"Doctor," Amy shouted from across the console room. "Stop. Explain."
"I did explain."
"Well, do it again." She glared and the Doctor cowered.
"I- oh, fine. Basically, the Cybermen and a demon and a criminal mastermind are all working together to, erm, bring down the entire planet. It's- ah- it's quite a problem, really."
Amy raised an eyebrow, trying and failing to conceal her horror. "And..."
"And we have to stop them."
She scoffed and started making her way down the stairs towards the mushroom-shaped console in the center of the room. "Right. So it's you, me, and the TARDIS against... what, did you say a demon? I thought there were no such things!"
With a worried look, the Doctor said, "So did I," and started adjusting settings on the console. He said something else, but it was too quiet for Amy to hear.
"Sorry, what, Doctor?"
"I said," he said, straightening with a triumphant expression, "it's not just us."
Frowning, Amy asked, "Who else is it, then? What, Rory and River? Oh, brilliant, we are saved." She rolled her eyes.
"No, it's-" The Doctor paused mid-word. "Although... Rory and River. Hmm. I hadn't thought of that." He pondered for a second. "No, it's a simply terrific team. You'll love them. And now, we should-"
"Doctor," Amy said, throwing an arm in front of the Doctor as he reached for another lever on the console, "tell me who they are."
The Doctor, sulking, replied, "Me."
Amy raised her eyebrows so high they seemed to be in danger of flying off her face. "You?"
He considered. "Well, not me me. Me from the past." He gestured vaguely with his hands in lieu of an explanation. "You know, wibbly-wobbly..."
She laughed bitterly. "So, we're going to stop Armageddon with you, me, the TARDIS, and you?"
"That was the plan."
"Blimey, the amount of ego there'll be in this room..."
"Hey," the Doctor said, face hurt, and flicked up an entire row of switches. "At least there'll be some intelligent conversation for a change."
Amy raised her eyebrows and looked shocked. "Doctor!"
He looked up at her and grinned madly. "Next stop, the post office."
"All ri- hold on. The post office?"
"I've got to send a message to past me somehow!"
Amy laughed, not quite sure if he was serious. It was so hard to tell with him most of the time. "And what, you'll address it to 'The Doctor, TARDIS, Space, Time' or something?"
He smiled at her. "It's a special post office. You'll see." And with that, he gave a very enthusiastic pull on a nearby lever, sending the TARDIS whirling through the time vortex. And as sparks flew everywhere and Amy tried desperately to hold onto a railing, he laughed and yelled, "Geronimo!" at the ceiling, feeling only enthusiasm for everything that was in store for the two of him.

***

"Remind me again exactly why you want to come with us?" John asked, raising an eyebrow.
Wrapping his scarf around his neck, Sherlock replied, "Boredom."
"Right," John said, unconvinced, and stood, reaching for his cane. "No ulterior motive or anything, then?"
Sherlock chuckled, bemused.
"Well," John said, rising from his chair, "let's be off, then. Lestrade and the team said they'd meet me there, so we might as well go now."
Sherlock nodded and strode out of the door without a further word. John, a slightly confused look on his face, followed him down the stairs and onto the street, only to find that his roommate was already halfway down the block.
"Sherlock!" John called, attempting to catch up. "What, are we going to walk to downtown?"
"Any other ideas?"
"We could call a cab. Eh- taxi!" John said, gesturing at a passing one. It pulled over to the curb and Sherlock, after quickly checking that a serial killer wasn't driving it- Lord knows that happened too many times to him- followed him into it.
John gave the cabbie the address that the email had specified and the two passengers then rode in silence until they reached it. Nothing needed to be said, although Sherlock was still struggling internally with the thought of telling John that he was in danger. He couldn't find the words and was honestly quite lost.
He didn't enjoy the feeling, and vowed to be honest next time.
Hopefully, there wouldn't be a next time, but...
It's fine that you didn't tell him, Sherlock. Fine. It'd be too sudden now, with ten minutes until 2:30. You waited a bit long, but it's too late now. But it's okay, Sherlock. It's okay.
And remember- emotions are a disadvantage.
Paying the fare, John left the cab first, looking around him. Hundreds of people filled the streets, although all of them seemed to be going in the opposite direction of the spot John had been directed to go to.
A buzz from his phone.
He pulled it out of his pocket and stared at the miniscule white text.
Running late, sorry. All is well?
John swore under his breath. Of all the times for Lestrade to slack off...
"Everything alright?" Sherlock asked, taking John's side and watching the frantic pedestrians, furiously analyzing every single one.
John shook his head, briefly contemplating texting Lestrade back and deciding against it. "Lestrade, with impeccable timing, has decided to be late."
"I'm not surprised at all," Sherlock said and turned away. "We should go."
"Oh- yes, of course, yes." And with a final concerned glance at the people going in what seemed to be the wrong direction, John followed his friend into a nearby alley. "So. Sherlock, I-"
"John. John Watson."
He turned and looked at the space where the voice was coming from. Standing right behind him was a very tall, very thin young man in a blue suit with energetic hair and a woman, slightly older-looking than him, with bright red hair and glowing eyes.
"D-donna?" John stammered as she threw herself at him in a hug. "But-"
"Oh, but this is brilliant!" she exclaimed.
"John?" Sherlock asked, but he wasn't looking at her. His eyes were locked with the tall man's.
"Donna and I- we- we went out. In, uh, year eleven." A slightly awkward pause. "So, er, is this-" John said, gesturing to the man, "is this your current-"
Donna and the man both wrinkled their faces and she laughed. "Oh, no, absolutely not, no. This is the Doctor. He's a- friend."
"You're not human, are you."
It wasn't a question.
The Doctor stared at Sherlock, elements of pain in his eyes. "How can you tell?"
"You're trying very hard to conceal it. I almost couldn't see. But I worked it out soon enough."
They appraised each other silently. "I'm the Doctor."
"Sherlock Holmes."
The Doctor's eyes widened. "You're Sherlock Holmes?" He grinned. "Oh, it is an honour. I've heard so much about you."
"I'm afraid I can't say the same about you, Doctor." And with a barely disguised disdainful glance thrown the Time Lord's way, Sherlock turned to John. "We should go."
"We'll go with you!" Donna said, looking pleadingly at the Doctor. "Are you two going to the- the- you know. The thing?"
Sherlock rolled his eyes and muttered something.
"We are, actually. You'd be welcome to join us," John said hesitantly.
"Brilliant," Donna said and, with another broad smile, set off after the others, who had already moved on to face the unknown.

***

"I'm assuming we're in the right place," Sam said, looking around him as he and his brother stood off to the side from the overflowing street.
"Yeah, I think so, too," Dean said, concern in his voice as he looked at the panicked faces of the flood of passerby.
"So... Should we follow them?" Sam asked, still unsure as to whether or not this was a good idea.
Dean shrugged. "Seems like they're all going in the same direction, so, yeah." They stepped away from the wall and were about to join the stream when Sam collided with a young woman moving away from where all the others were going.
"Oh- oh, I'm really sorry, " she said and smiled. She had a melodious English accent and a lovely face. Sam noticed this and smiled back.
Dean rolled his eyes.
"No problem, "Sam said. "Hey, uh, since we're here... Are you going to the same place all these people are going?"
The girl raised her eyebrows. "No, I- I've been told to go somewhere else."
"Told?" Dean asked, joining the conversation. "By who?"
"Well, the email," she said, as though Dean and Sam were supposed to know what she meant. "But I'm assuming you didn't get one?..."
Sam shook his head. "We're not from around here."
"Yes, well, I can see that," she said and smiled again. "I got an email telling me to be at a certain place at 2:30 today or... Or something bad would happen to my family. So." She sighed. "I don't care if it's a trap. I'm willing to take that risk for my family."
"Wow," Sam said quietly. "So this place. You said it's not where all these people are headed to?"
The girl shook her head. "Opposite direction, actually."
Confused, Sam said, "That's got to mean something."
"Yeah, that's what I think." The girl squared her shoulders. "I'm going, though. I have to."
"No matter how dangerous it might be?"
"Exactly."
A pause. "We'll go with you."
"Sam!"
With a glance at his brother, Sam said, "It's kind of our job to protect people, and-" Ignoring Dean's jabs to get him to shut up, he went on. "And we- think- there might be something dangerous waiting for you there. Actually, we're pretty sure. So, we-"
"I'm just one person, though," she said, gesturing to everyone else on the street. "What about all of them?"
"They're our next mission," Sam said, and the girl smiled.
"All right, then." Glancing at her watch, she said, "We should go. It's nearing time."
"I'm Sam Winchester, by the way," Sam said, extending a hand.
"Martha. Martha Jones." They shook hands, holding on for just a bit too long.
"And I'm Dean," Dean said, "if anyone cares."
They set off, Sam and Martha slightly ahead of Dean, conversing. Dean, as much as he wanted to annoy Sam by intruding, thought better of it and left them alone. The girl seemed nice enough. Relatively harmless. Why not let Sam have a bit of fun for a change?
"So you said you went to Stanford?" Martha asked.
"Yeah, for a little while. And then... I dropped out." Sam looked away.
"Why'd you leave?"
Sam shrugged. "Family issues is the best way to describe it, I guess." He took a deep breath to dispel the sudden pain inside at the memory of Stanford and of Jessica. "What about you, Martha? Are you in school?"
"Just left medical school," she said and grinned. "I'm a proper doctor, now."
"Not bad," Sam said. "Maybe that'll come in handy later today."
Face suddenly grim, Martha nodded. "Yeah, I think so." She sighed. "I don't want to say I'm scared, but..."
"You're terrified, aren't you?" Sam asked softly.
She nodded. "It's not a feeling I like."
"I know it well," Sam said, thoughts flashing to all of the horrible things that had been happening lately. "But at least you're not facing it alone, right?"
Martha stopped and looked at Sam. "You're right. I'm not." They kept eye contact for a few seconds until Sam noticed Dean out of the corner of his eye pretending to gag. Rolling his eyes at his brother, he set off again. Suddenly, four dark shapes darted across an alley in front of them.
"Hey, Dean?"
"Yeah?"
"Be ready, okay?"
"Gotcha."
Placing a hand on the gun tucked into his jacket, Sam moved more cautiously. Martha looked at him inquisitively. "What is it, Sam?"
"I just- I thought I saw some people. That's all. It's probably nothing."
The shapes appeared and vanished again. Sam's hand tightened on his gun. "Hello?" he said, ready for anything.
Nothing.
"Is anyone there?"
A single shape emerged from the darkness around twenty feet away, silhouetted against a distant wall.
"Stay back," Sam whispered, but Martha had already started forward, something different in her eyes. "Martha!"
Voice teary, she called, "Doctor?"
"Martha? Is that you there?" the shape called in a cheery voice.
"Martha?" Sam said, unsure of what was happening.
She turned back to the brothers, smiling through tears. "It's fine. It's- it's a friend of mine." She and the shape both set forward at the same time and met.
"Hello, Martha," the shape, which was actually a tall, thin man with spiky hair and a blue suit, said warmly.
"Doctor." She smiled. "Long time no see, eh?"
He grinned. "Oh, come here." They hugged firmly.
Exchanging looks, Sam and Dean released their holds on their guns and straightened. Dean cleared his throat.
"Oh, it's good to see you, Doctor," Martha said and released him. "I'm glad you could come. Where's Donna?"
"Right here!" called a voice from around a corner.
"She's tying her shoe, I think," another voice said.
"Who's that?" Martha asked.
"Someone who's going to the same place you are," the man said. Looking at Sam and Dean, he asked, "So who are your friends here, Martha?"
"Oh! Doctor, meet Sam and Dean Winchester."
"Hiya, Doc, how ya doing?" Dean asked, shaking the hand that the Doctor had extended.
The Doctor wrinkled his nose. "No, no, don't do the Doc thing..."
"Sorry," Dean said, not sorry at all.
"They're here to help, apparently," Martha said. "To help with... You know. What's going to happen."
"Good," the Doctor said and smiled. "Looks like we've assembled quite the team here."
Just then, three more people appeared around the corner; a short red-haired woman, a very thin, slightly alien-looking man dressed in black, and a man with a sweater and a cane.
"Donna!" Martha said, smiling, and the women hugged. "Good to see you again."
"And you." Eyes alighting on Sam and Dean, Donna's eyes widened. "Who are they?"
"Oh, uh, that's Sam and Dean," Martha replied, knowing what would inevitably come next.
Approaching the brothers, Donna smiled. "Hi. I'm Donna."
"Uh, hey," Dean said, uneasy.
"I'm John Watson," said the man with the cane. "This is Sherlock Holmes."
Donna and Martha turned around simultaneously. "What?" Martha gasped. "Sherlock Holmes? The Sherlock Holmes?"
Sherlock, a wry smile dancing across his mouth, nodded.
"Whoa," Donna said, completely star-struck.
Confused, Dean asked, "What's the big deal? Who is this guy?"
Everyone ignored him except Sam, who said, "The best detective in the world, they say. Apparently, he can tell almost everything about you just by looking at you once." He looked at Sherlock admiringly. "I've always wanted to meet him."
"Everything, eh?" Dean said, somewhat unimpressed. "I'd like to see him try with me."
Sherlock raised his eyebrows and took a deep breath. "I can tell that your mother died when you were a child, violently. After that, your father went insane over finding revenge, but- ooh, he's dead now, isn't he? So now you and your brother, with whom you have an extremely unhealthy codependence, are trying to track down his killer, who is also your mother's killer. You're an alcoholic who is terrified of commitment. You have one-night stands only for fear of her getting attached and getting hurt when you leave or she finds out the truth about what you do which is- hunting. You hunt things. You're very good with a gun and you're very good with cars. And-" Sherlock squinted in concentration. "How many times have you died, three? Two?" He looked Dean up and down again. "Can't keep a job. Well, never tried to get a job. Dropped out of high school, didn't go to college. You were furious when your brother did. Furious and heartbroken. And jealous. And, what's more, you know that your father really never-"
"That's enough," Sam interrupted, seeing Dean's clenched fists and that he was fighting hard to keep back tears.
Silence.
"Son of a bitch," Dean whispered. "How-"
"It's written all over you," Sherlock said. "You should really work on hiding your past. I'm sure that makes it ever so easy for all of those demons and ghosts and things to get to you."
Dean's mouth opened in shock but no words came out.
"Wow," said everyone else in unison.
Sherlock smirked.
Dean blinked and turned away.
Conversations began and Sam pulled his brother off to the side. "Look, Dean, it's okay."
"No, it's not!" Dean said, still visibly upset by this stranger's violation of his past. "I mean, did you see that? That was- that was, like- I bet he's a mind-reader."
"He's not a mind-reader, Dean, he just... I don't know. He deduces things based on the way your sleeves are rolled up or something."
Dean shook his head. "I don't know, man. Whatever it is, it's creepy."
Suddenly, a loud beeping sound started echoing off the walls of the alley.
"Someone's phone?" Dean asked, looking around.
The Doctor, flabbergasted, stared at his sonic screwdriver and psychic paper. The sonic was the one emitting the sound- it was one he'd never heard before. "Someone's trying to send me a message," he said. "Who, though? I'm the only one who knows how to control this technology!"
"Well, what does it say?" Donna asked, leaning over to take a look.
"It says... That I need to be here right now. Well, that's helpful." He looked around him. "Whoever sent this should be here any second now."
Nodding at Sam, Dean drew his gun. His brother mirrored him.
A loud whooshing noise filled the alley as a wind started to blow. A bright light was flashing a few feet off the ground.
"No," the Doctor said, eyes enormous. "No, no, no, no, no, this cannot be happening!"
A tall blue box appeared, seemingly out of nowhere. Sherlock looked intrigued, Martha, John, and Donna confused, Sam and Dean prepared to take down this magical teleporting object, and the Doctor terrified.
The whooshing stopped and the box materialized fully, becoming solid.
The doors swung open with a creak and everyone inhaled sharply in anticipation.
Suddenly, a lanky man in a tweed coat and a bowtie sprung out, followed by a very attractive red-haired girl. "Hello, everyone! Looks like you got my message. May I speak to the Doctor, please?"
After a very tense pause, the Doctor took a step forward, absolutely furious. "Y-you can't do this. I know who you are, and you cannot do this."
"I think that you'll find that I can. Good to see you again, by the way." The lanky man grinned. "I missed you."
"Stop it. Stop it right now." The Doctor took a shuddering breath as he tried to control himself. "This isn't supposed to happen. Ever. You, of all people, know the consequences."
"I remember this, and it is." Turning away from the Doctor, the man looked at the people staring, confused, at them. "Oh. Oh, my. Yes, you'll all do very nicely. Now, we have to go. They'll be here any minute now, and-"
"Hold on a second," Dean said, still holding his gun. "Who the hell are you, anyway?"
"Did I forget to introduce myself?" the man said, smiling. "I'm the Doctor, and this is Amy."
A pause as everyone looked from one Doctor to the other and the Winchester brothers stowed their guns.
"Hi?" Amy said meekly.
"I thought... he was the Doctor," John said, gesturing to the one in the blue suit.
"He is. The other one is the same man, but from the future," Sherlock said.
"Same man?" John said. "But he doesn't-"
"Regeneration," the new Doctor said. "Bit confusing, I'll explain later."
"Wait, Doctor, this is you?" Donna said. "My, you've really let yourself go..."
"Oi," the Doctor in the bowtie said, smiling. He looked at Donna, then, and his face changed. Eyes filled with unexplainable pain, he said, "Oh, and it's good to see you, Donna."
"Uh, thanks, Doctor," Donna said, surprised by this Doctor's strange reaction to her.
"Doctor, we've got twenty seconds," Amy cried, looking at a stopwatch on her wrist.
"Oh, really? I thought we had more time. Hmm." He became animated and pushed the doors of the box open. "All right, looks like we'll have to take everyone. Get in, we're almost out of time!"
Amy went in, and Sherlock followed without a word, although he was simply on fire with curiosity inside. Knowing better than to doubt his friend, John went after him. Sam and Dean, confused, watched as they somehow fit into the seemingly tiny box. Sam shrugged and went in, and Dean did the same after a second or two. With a glance at the blue-suited Doctor, Martha joined them, leaving the two Doctors alone outside of the box.
"After you," the new one said.
"I'm begging you," the first interrupted, pleading. "Don't do this."
"For the planet, Doctor." The new one smiled grimly. "If you don't help me now, it dies. I can see it and I know that you can too."
The old Doctor's face fell. "I-" He ran a hand through his hair. "I'll never forgive you for this."
They looked at each other, and the newer one grinned. "Well. That will be a problem in a few centuries, won't it?"
The older one sighed and, eyes still brimming over with anger, pushed past the other Doctor into the box.
With a final smile, the new Doctor stepped in and closed the doors behind him.
"Allons-y, then," he said quietly and straightened his bowtie.