Author's note: Review please.

Greg's first impulse, calling Sherlock, was no help. It would have been a case the consulting detective would have enjoyed, whether his brother had forced him to take it or not.

He knew Moriarty was aware what he was thinking; the gleeful expression on the man's face was enough to prove that.

"So" he said, not only to break the silence, but also to distract himself from the consulting criminal's stare, "There has to be an emergency unit or something like it. To bring him back".

Mycroft nodded. "Most likely activated by a sensor he keeps on his person."

That would be a problem. Even if they found this device, if it existed at all, and they managed to activate it without help, it could only bring Trevelyan back because he knew about it.

And they had to hold on to their memories while they were doing so.

They would have to see if Moriarty made things easier for them. He thought it more than likely that he wanted to get Trevelyan, if only for revenge; but maybe revenge was too boring for him...

He really wished Sherlock was here. Sherlock had fought against him and won. But he wasn't here, and Greg would have to do the best he could.

"It is going to be difficult to find" Moriarty announced. "And remembering..."

Greg wanted to shout at him to be silent, but it wouldn't bring anything, and he resigned himself to sit there quietly, feeling the other man's stare at the side of his head.

Apparently Moriarty was trying to get him to lose his temper. He probably thought it fun.

He took deep, even breaths and began, "Trevelyan doesn't trust anyone."

He had gathered as much from the lab and the files that had clearly only been read by a few people, and by the fact that not even his employers knew what he was working on.

Mycroft nodded.

"It will be hidden somewhere then, not being kept by another person – "

Sherlock would probably have rolled his eyes and commented "Obviously", but Mycroft listened to him patiently. Perhaps he hoped that Greg talking would help him figure it out, like John talking often did in Sherlock's case.

"I think we all agree on that".

Moriarty had to comment, of course. For a moment, Greg considered locking him into a room – Mycroft's house must be the safest in the city – but God knew what he would do once he was alone.

They would have to take him with them.

Greg vowed to keep him in view at all times.

"Do you think he keeps it at home?"

Mycroft shook his head.

"It's the first place anyone would look."

He brought his hands up to his face in prayer position, and it reminded him so much of Sherlock that Greg's throat constricted.

Moriarty didn't say anything, but the DI, who was keeping his gaze firmly on the elder Holmes while making sure that he didn't move out of the corner of his eye, thought that he probably enjoyed the show.

"It would have to be a place he knows" he said. "I am sure the Secret Service keep him under surveillance. He is rather valuable, is he not?"

The right side of Mycroft's mouth turned slightly up, and Greg knew it was the only smile he was going to get. As the British Government grabbed the file and began to peruse it again, he couldn't help but notice that Mycroft was slower than usual; and that it most likely had nothing to do with his age, even though Sherlock and John laughed every time one of them alluded to it, for reasons he couldn't quite grasp.

The fight against the memories must take a lot out of him. Since he was very intelligent, he probably could remember things more clearly than most, and therefore the wrong memories had to be stronger.

Wrong. Right. The words made less and less sense the more Greg used them in this context, and he quickly turned to keep an eye on Moriarty before he forgot what had happened.

The victorious glint in the consulting criminal's eyes made it easy to see that he had foreseen their struggle; but at the same time, he couldn't help but think that normally he wouldn't have shown it.

Moriarty hated Trevelyan. He was sure. It didn't surprise him. Sherlock had always hated any interference in his life, even when it came to drugs (before they came to see each other as friends, but he couldn't think about that now, because whenever he did, a cold feeling in his chest reminded him that he might never see him again) and Moriarty was his mirror image – what would have happened if Sherlock had chosen a different path. Greg suppressed a shudder at the thought.

Then again...

No, the man he knew couldn't have become such a monster. His friend would never have turned into this.

They had to clear up this mess. Moriarty's stare was mocking on, daring him to say something, anything.

"Do you have something?" he asked. It wasn't smart to do so – Mycroft preferred to tell people in his own time what he knew – but he didn't want to follow his trail of thought, because he would only get more and more scared that they would never get Sherlock and John back if he dwelled on them being trapped in a parallel universe, or he would start to remember and he couldn't allow that to happen.

Mycroft frowned.

"He left his house during the night on several occasions, and was followed until he managed to escape the agents somewhere near the Thames. He had always returned by the next morning, so it wasn't considered important."

Greg sighed.

"I do believe – "

Mycroft quickly took out his phone and checked something.

"There are a few houses that would allow him the privacy he'd need in the vicinity of the place he went missing. Where there aren't any neighbours to – "

He trailed off, going through the maps, Greg assumed. After a few seconds, he announced, "This one. It is the most likely option".

Greg nodded.

"So if we do find the device or whatever Trevelyan left... What do we do?"

Mycroft didn't look at him. Instead, he looked at Moriarty.

The consulting criminal shrugged his shoulders. "Are you asking me for help?"

"I am considering the possibility that Trevelyan must have told you what to do in case he doesn't return. He saved your life and you know that, shouldn't you help him, he might change other things."

"Maybe he would kill me off again" Moriarty suggested. Was that wistfulness the DI heard in his voice, or was he only imagining it?

"No. He wants you alive. He is clever but he doesn't have your... qualities. I suspect he wants to –"

"Take over the city?" Greg asked, confused. He hadn't meant to say it out loud, but the theory had shaped itself in his head, almost without him noticing.

"It has been rumoured that Trevelyan has strong opinions about how the country should be run" Mycroft replied simply. "He believes science is everything. He doesn't care for diplomacy and politics."

"But then why – "

He didn't have to finish his question.

"Balance" Mycroft answered. "There has to be an equilibrium. Trevelyan loves order, therefore he needs someone who loves chaos to help him take over."

Moriarty didn't correct him, but he didn't confirm that his suspicions were true either. Mycroft hadn't waited for it anyway, apparently, since he continued, "Trevelyan told you what to do."

"You mean in case something happens – for example a consulting detective and his faithful blogger – and he finds it difficult to return?"

Moriarty's eyes glistened.

"Of course."

They were dependent on him, and it was a feeling Greg didn't like. If Moriarty knew how to handle the device – and they had no proof – he might simply return Trevelyan and leave Sherlock and John where they were.

If Greg was right, and Moriarty hated Trevelyan, it still didn't mean that he would help them. In fact, there was every reason to think he wouldn't.

But it seemed that the consulting criminal was their only chance. Of course Mycroft could find specialists, and they might be able to find out how the device worked (supposing they found it) but they didn't have much time. Either they would forget what had happened, or Trevelyan would change more.

Neither of them asked Moriarty if he would help because they both knew he would only enjoy their questions and not give an answer; a few minutes later, they were on the way to the house that, as Mycroft explained, was rented under the name of a distant relative of Trevelyan's.

Greg felt the gun in his pocket. There wouldn't be any guards – not if Trevelyan was as secretive as they thought he was – but there might be traps.

There was only one way to find out.

Soon enough, they stood in front of the house.