Sherlock quickly dismissed the thought that what he was seeing was impossible. John was right beside him, experiencing the same, and it was far too logical, far too real to be a hallucination.

Plus, they had been in a laboratory whose existence was kept a secret. It wasn't impossible that what people had thought of as impossible could happen while they were there.

"Sherlock?"

John had moved closer to him, staring at the other version of himself. Sherlock couldn't blame it. It must be a shock. The consulting detective, while he was surprised to see William Holmes acting like a normal person, obviously having a good relationship with his brother – as shown by him calling him after he'd had a fight with his flatmate – and a job that was recognized by society as such, it didn't shock him. Since Moriarty, he had a new appreciation for sentiment, for being human, and if he happened to be so in an alternate universe – or wherever they had landed – he supposed it wasn't that bad. After all, he was the John in this version.

But John – he saw himself being what Sherlock had been before they'd met. And –

Sherlock frowned.

This wasn't right.

He had changed after Moriarty. After three years alone. He had stopped trying to convince himself that he was a high-functioning sociopath.

So why was John still acting like he was?

Maybe Moriarty was alive.

Sherlock took a deep breath and felt John move even closer to him. Of course his flatmate would notice that he was disturbed by the theories running through his mind.

"So" the other John interrupted his thoughts, "Since it is impossible that you are hallucinations – it would be impossible for us to see and hear exactly the same – we need to figure out what happened. Tell us what you did before Lestrade found you".

Sherlock huffed, annoyed. Of course they had to analyze the situation, but there was no need to treat them like a child. Without sparing the man a glance, he walked over to the fireplace, realizing that the chairs had been switched – or rather, that this John still preferred a more comfy chair, even if he was acting like he didn't care about anything other than his experiments (and he didn't remember, he forced himself not to remember, it wasn't important) – but not caring as he sat down in his usual place. They had to prove that they were indeed real – certain doubts must linger, had to linger, because ordinary people were convinced there was no such thing as "parallel universes", and Bill and Lestrade still looked like they couldn't make sense of what they saw – and that they were different.

Because if they didn't, John would refuse to take his opinion seriously, Bill would continue to try and make sense of their existence, which was as senseless as it was unnecessary, and Greg would probably make fun of it all, because obviously he didn't care much for what happened.

Strangely, it was this that distracted Sherlock the most. He could live with watching himself stumbling around like any other human being; he could live with John being brilliant. But Greg not caring –

Now was not the time for sentiment, he reminded himself. They had to stop asking questions that led them nowhere and work together.

The other John raised an eyebrow.

"I usually sit here" Sherlock said. He knew he'd be able to deduce what he meant. His behaviour didn't allow any other conclusion.

He was right. John slowly walked over to the chair opposite him and sat down. He leaned forward, his chin resting on his right hand.

"So" he stated slowly, "you two are – "

"From a parallel universe" Sherlock interrupted him. "At least it's the most plausible theory."

John narrowed his eyes.

"You don't work in a lab, like Bill does. You spend a lot of time at St. Bart's, as well as Scotland Yard. You experimented on a lung less than twenty-four hours ago."

For a moment, he was silent. Then he continued, "You are a consulting detective".

Sherlock nodded.

"The only one in the world – our world. I – "

"Invented the job" John finished, standing up and brushing off his suit. He started pacing.

"People do not suddenly appear in different universes, dimensions, or worlds" he explained, "it is impossible that no one would have noticed. Something happened. You were sent here, but based on the fact that Lestrade and Bill brought you here without giving any explanation, you didn't give any, which you would surely have done if you knew what. Therefore, you arrived here unexpectedly. Any theories?"

Sherlock had patiently waited for John to finish his monologue, being aware that he would not appreciate being interrupted, and quickly glanced at his John, who was watching him with a mixture of amusement and annoyance.

He quickly waved at him to sit down – there was no reason for the doctor to remain standing, clearly none of the three other people in this room were a threat – and began.

"We were investigating a certain Doctor Trevelyan, who was most likely involved with the Secret Service, but had apparently started to use volunteers for dangerous experiments."

"How did you learn about Trevelyan?" John asked. "And how much time did you need to deduce everything? It took me several months to understand why members of my homeless network disappeared and returned mad –"

"You mean over a year" Bill corrected him automatically, and Sherlock realized this was his equivalent of John calling him out on the few mistakes he'd made during investigations in the last few years, to remind him that he wasn't always right. But that wasn't what had him sit completely still, his gaze fixed on the wall.

John had mentioned his homeless network.

That in itself wasn't shocking. It seemed only logical. A homeless network was the quickest and most practical way to gather information.

But Sherlock had never thought, not for one moment –

That Greg Lestrade, that his DI, could be part of it in this universe.

It was idiotic of him, of course; all the signs had been there. It was obvious. Greg running around on the streets, frequenting pubs, the allusions to "errands" he ran for John –

And yet Sherlock hadn't drawn the conclusion because he found it difficult to see anything but the DI in him. Seeing John brilliant but rude he could deal with; seeing himself ordinary he could deal with. But his DI, the DI who'd arrested him and then offered him to work with him, the DI who'd watched over him, often against his will, on danger nights, the DI who had warned him before he was going to arrest him, homeless and having given up on himself and his life, to the point of not caring what happened to John, to him –

Normally, this was the type of man Sherlock would gladly have in his homeless network. The type of man who followed a lead anywhere because he needed the money.

But this was Greg. And it wasn't right.

"You alright?" the very person he'd been thinking about asked, tilting his head to the side. "You're staring at me funny".

"Obviously you aren't part of my network in his universe. Boring".

Sherlock had his confirmation. Whatever cases John and Bill had worked on – they had never met Moriarty, John had never faked his death and spent years apart from his friends. Otherwise, he wouldn't have talked that way.

He realized that he was thinking in a way that he would have scoffed at before he met John, and that this John would scoff at now. He didn't care.

"What was I?" Greg's voice broke through his thought process.

"You know me. So, what was I? Drug dealer? Murderer?"

He sounded too cheerful in Sherlock's opinion, but there was nothing he could do about it, so he replied courtly, "DI."

Greg laughed.

"Me? A DI? At Scotland Yard? Let me guess, bowing to your every whim, like Gregson does?"

So Gregson was still working for the police, Sherlock noted.

"You help us" he answered quietly, and saw that this John was confused by his reply, but didn't care.

"I bet" Greg remarked sarcastically.

John opened his mouth, but his counterpart talked first.

"It doesn't matter. You didn't answer my question."

"My brother, Mycroft, forced me to take the case."

He might have enunciated the British Government's name more than he had to – in fact, when they had been children, he'd often used the abbreviation "Mike" to annoy him – but he felt it was necessary. Everyone in the room had to accept that, while looking the same, they were different people with different lives.

"Mike? He forced you?"

Bill shook his head.

"He wouldn't – "

"Your brother obviously isn't the same as this man's" John said, impatiently. "Let him continue".

It confused Sherlock that Bill simply stopped asking questions without any sign that he was angry. The consulting detective had been dismissive of John and his relations, but despite his and Harry's complicated relationship, the doctor had never failed to tell him that he thought his comments inappropriate. Although what he deemed inappropriate might depend on how well he and Harry got on at the moment.

He watched as Bill sat down on the sofa, completely unconcerned with his best friend telling him that the brother he had been about to see when he'd run into them wasn't an important topic in this discussion and Greg deciding to sit down beside him, studying them as if he was bored and needed entertainment.

Their roles weren't just reversed, and this wasn't simply Greg as a member of his homeless network, he realized. He had almost made the same mistake he was trying to get the others to avoid – looking upon them as nothing but copies, being convinced that Bill was like John and John was like him. It would be easy, it would be tempting. It would be human error, and Sherlock refused to let it happen when he needed to gather his thoughts to get him and John back home.

"Mycroft is the British Government" Sherlock's John decided to explain, probably because Sherlock hadn't answered yet, too busy watching Bill's reaction, much to this universe's John obvious annoyance, if his expression was anything to go by, "and he suspected that something was going on. So we broke into the lab – "

"We heard noises" Sherlock continued. "We went to see what was going on, but sadly were knocked unconscious; when we woke up, we were here."

"And then I found them and brought them to you. I think that warrants extra payment" Greg happily announced.

"I do not think that you have done what you were sent out to do. There is no reason to pay you".

The – member of John's homeless network shrugged his shoulders good-naturedly, showing he'd expected this reaction.

John sighed. His shoulders slumped for a moment before he stood up straight, and Sherlock shot his friend a glance out of the corner of his eye, to find that his gaze was flickering between his counterpart and the consulting detective, most likely comparing John's movements to Sherlock's when he was annoyed at someone.

"Let's get back to the topic, shall we?"

"Like I said" Sherlock replied, "We don't know what brought us here."

"Did you search the lab?"

"No."

"Why not? It might have – "

"We had been knocked unconscious. We wanted to get home".

John sounded hostile, and Sherlock bit his lip. He didn't want the doctor and his counterpart to fight. Naturally, it was almost inevitable that they did so – John might have been able to accept this John's attitude because it reminded him of Sherlock, but what he wouldn't be able to accept would be the dismissive way in which he treated his friends. Sherlock hadn't acted like this ever since he returned.

He wanted to interfere, but as soon as he saw that the other John's spine had straightened, he knew it was useless.