Author's note: I'm so happy. So many reactions to this fic... I feel so honoured. Knowing that people read my stuff makes me so glad... Thank you. Thank you a thousand times.

I don't own anything.

„You can't be seriopus!" John exclaimed, after he had let Trevelyan's theory sink in and realized that Sherlock didn't consider it utterly impossible. The consulting detective understood why. The theory was so strange to be almost called ridiculous; and yet –

Maybe it wasn't much stranger than a machine implanting false memories in Mycroft's mind. There were several theories about choices and decisions creating parallel universes where a different choice created a different outcome; Sherlock had read about most of them. And, if they couldn't be proven, they couldn't be disproved, either; no one could say with certainty that different universes and dimensions didn't exist.

And his brother was adamant that what he was remembering was the truth, despite his skills at deduction, despite every proof to the contrary.

The question was: If this Mycroft came from a parallel universe where he had taken Sherlock with him and raised him –

Where was his brother?

The logical answer was that he was caught in the universe this Mycroft came from. And it was clear that the shock had caused some damage to the portal.

They might be stuck with this Mycroft. His brother might be stuck in another universe.

Sherlock suddenly wished he could dismiss the idea as easily as John had done. Because if it was true – if Trevelyan had indeed sent Mycroft to another universe – he would never see him again.

It was, in some ways, worse than his brother dying. Dying implied the normal end of life; Sherlock understood death, knew what it meant. But his brother being caught somewhere, alone, most likely just as confused as the Mycroft that was currently occupying his mansion...

A strange wave of possessiveness hit him when he realized that would mean Mycroft would meet this other Sherlock, the Sherlock who had never taken drugs or insulted him in his life, and that he would probably prefer him to the brother he had.

Sherlock had always tried to distance himself from the brother who left him behind – the brother who forced him to stay – and yet – and yet –

John would call his thoughts "human", without a doubt; Sherlock knew that sharing the same genes didn't automatically mean he had to care for Mycroft, of course. This was just a silly old prejudice.

But his brother had to return. He had always been there, even when Sherlock had resented him for forcing him to stay in his house after detox, for kidnapping his friends, for telling Moriarty his life's story – he didn't resent him for any of those reasons anymore, it would have been childish, really, but still, Mycroft had always been a constant in Sherlock's life. A life filled of uncertainties and tries not to care for anyone, and Mycroft had been there, no matter that he hadn't taken Sherlock with him, hadn't helped him escape when he went to university.

He had always been there, and suddenly Sherlock was confronted with the possibility that he might be gone – that he might never have been there.

This Mycroft (if it was a different Mycroft; there were other possibilities he had to acknowledge – he might simply have lost his mind) – he was so – nice, polite, considered. He might be the brother Sherlock had wished for once upon a time, but he wasn't the brother he had lived with, he wasn't the brother he needed right now.

Simply because –

Sherlock was the wrong brother for him.

Sherlock had been left alone with their parents – and the less said about them, the better – when he had been just eleven years old, he had taken drugs, he had been through withdrawal, he had been forced to stay in Mycroft's house, he had become a consulting detective even though his brother had thought he should rather have been a scientist or a philosopher, he had lived in 221B Baker Street, he had suffered through Mycroft kidnapping all of the friends (it had taken a while, but now he admitted that this was the correct term) he made, he had hidden and tortured and killed and fought to get back to the life he'd known...

He hadn't lived with Mycroft, he hadn't studied, he had quit university; if his theory was correct, he wasn't this Mycroft's Sherlock, and he would never be. Just like this Mycroft wasn't the brother he knew, nor the brother he needed. His Mycroft would let him be, would let him investigate crimes, steal evidence without a thought; this Mycroft – he wouldn't understand why Sherlock would want to solve crimes in the first place. He would try to reason with him, make him see that what he was doing was dangerous, that he should go back to university and become a scientist. He wouldn't understand his need to solve crimes, like his Mycroft did. He would simply not understand anything.

And he would expect Sherlock to live with this, because he believed that he had raised him. He would expect Sherlock to be the brother he remembered, and he just couldn't be.

He looked at Trevelyan, who seemed to be just as shocked as Sherlock and John were, and fro good reasons. While Sherlock didn't blame him – he understood the need to search for knowledge – having someone like Mycroft Holmes collapse and just possibly replaced in his laboratory could hardly be easy. Nevertheless, he had hurt his brother, which definitely made it difficult for Sherlock to feel sympathetic towards the man (although he would certainly never admit as much to his brother, his real brother). He had answered all of Sherlock's questions, however, and he hadn't lied about his theory – a theory that could have brought him in an asylum at a different time – and that was something, even if Sherlock still couldn't understand how he could have allowed someone as important as Mycroft Holmes somewhere near his machines. There were too many variables; too many choices. How could he ever have thought that instructing people to simply try it out was safe?

About despite everything, Sherlock needed his help. If Mycroft was indeed stuck in another universe – if he was lost in a world that could have been – his only way out was the way he'd come in, and that meant Trevelyan had to repair the Choice Portal.

He told the scientist as much, in a voice that brooked no argument, while John was standing beside him, still sceptical but supportive, just like he had always been. Trevelyan seemed unsure if he could do it, but still happy not to be persecuted immediately, and he eagerly promised that he would work night and day to make the portal work again.

Considering just how many people relied on Mycroft, it was probably better.

Considering what Sherlock felt, seeing his brother – or not his brother, the situation was rather complicated, even for him – this lost, it was definitely better for Trevelyan's well-being.

John didn't say anything as he told Trevelyan how to proceed. He only spoke after they has caught a cab.

He looked at Sherlock and asked, "Are you sure about – about this parallel universe thing?"

Sherlock wished he could tell him that he was, but the truth was that he didn't know, so he shook his head. "It's a possibility".

"A very remote possibility" John argued, shaking his head. "Sherlock, I know it's easier to believe your brother is somewhere – even in another dimension – than that he has simply lost his mind, but still..."

Sherlock bit his lip. Of course his theory could just be wishful thinking; in a way, it was easier to imagine Mycroft, his brother, caught in a parallel universe, and Sherlock able to get him back, rather than telling Mycroft about Moriarty and the role he had played in his last scheme.

Yes, it would definitely be easier to pretend that this Mycroft, this Mycroft who was so fond of him, knew nothing about his games with the consulting criminal.

But still, it was a theory, and a theory he couldn't disprove at that.

John apparently read his thoughts, for he added, "I know – trust me, I know what it means to imagine that you can fix your sibling simply by pressing a button".

Sherlock looked at John, but the doctor had turned to look out of the window, avoiding his eyes. Of course John knew.

Sherlock cleared his throat. "Anyway, we have to consider the possibility that Mycroft may be caught in parallel universe, as long as we don't know for sure".

John didn't look at him, but he grasped his hand and squeezed it, just for a moment, and this told Sherlock that the doctor would stand by him no matter what.

He hadn't really known what to expect when they returned to Mycroft's mansion, but it certainly wouldn't have been his brother (or not his brother; it was rather confusing, even for him) making dinner, asking whether everything had "gone well".

He didn't know what to say, but thankfully, John took over and told Mycroft about the portal that had suffered some damage (although he didn't mention Sherlock's theory about parallel universes, which was probably for the best). Mycroft seemed to take it well enough, he listened and nodded, even though he shot Sherlock a few worried looks. Naturally, he didn't care about John; he didn't remember John, he didn't know John, and even if he had, the doctor would simply have been the flatmate of his brother.

"John" Mycroft started after the doctor had finished talking, "I'm done here; could you lay the table for me?"

John knew what the elder Holmes meant; he obviously wanted to talk to Sherlock alone. While he didn't think it would do much harm – Sherlock would tell him everything that had happened anyway – he wished he could stay regardless. He looked at the consulting detective, who gave an almost imperceptible nod to make him understand it was all fine, and left the kitchen.

Mycroft took their dinner of the stove and made sure it was safely stored until they would take it to the dining room and John before speaking.

"I looked up everything we had Jim Moriarty".

Sherlock tensed. He should have expected it; he really should have. It was only natural for Mycroft to want and find out everything about him. After all, he would want proof that Moriarty had been a psychopath. He was a Holmes – no matter from which reality – and a Holmes always wanted to make sure.

Mycroft turned around, and Sherlock, to his surprise, saw nothing but regret and – was this sadness? – in his eyes.

"I'm sorry" his brother said, "If I had known – I would never have asked about him. I wouldn't have made you remember him. And I certainly – "

He stopped, and Sherlock knew what he was thinking about. The files he had read must have contained information about his talks with Moriarty; Sherlock should have known that he would try and find out everything. And now Mycroft was trying to apologize to him, for something he really didn't have to apologize in the first place.

So he simply answered, "I know".

"I don't think you know". Mycroft's gaze bored into his, earnest, wishing to be forgiven, which Sherlock couldn't do, simply because there was nothing to forgive.

"I'm still sad he died" Mycroft continued, "I can't help it. Not with everything I remember. But... I know what he did to you." Sherlock nodded.

Then, suddenly, Mycroft hugged him, and Sherlock didn't know what to do, so he decided to hug him back, albeit stiffly. Mycroft patted his back before withdrawing.

Then, he repeated, "I'm still sad about his death. I can't help it".

He abruptly turned around and Sherlock answered, quietly, "I understand" because he did.

Mycroft gave him a small smile before putting a bowl into his hand and making his way to the dining room, Sherlock following him.

Author's note: I needed to write the scene with Sherlock and Mycroft – I love brotherly bonding. I can't tell how much longer this story is going to be. Sorry.

I hope you liked it, please review.