It was galling to be stuck in London, a physically offensive sensation that grated at every nerve. Two days ago he'd yearned to be back here, but now the familiar streets and faces and sounds were like a cage, penning him in. And Mycroft held the only key.

Sherlock had been happy to bid good-bye to Paris; now he would have given anything (almost anything, not John) to get back there.

Paris needed him now, and he'd made the foolish mistake of stepping away from it, of coming home, only to be ensnared by Mycroft's machinations, by John's reasonable assertions that if Alexandre Georges had been targeted, it may have something to do with them, and they were safer here, where they had protection.

But the crime hadn't happened here, and he had no access. He had no Lestrade in with the gens d'armes, nor Hassard, nor any of the others. No one he could wheedle for information. No one who needed his assistance – no, no one who wanted his assistance, because it was needed, now more than ever, for an innocuous man whose only connection to Sherlock was a faked letter.

The damned letter. It had been the first thing he'd asked about – the baby had been the first thing John had asked about. She was fine, predictably, at home with the mother when Georges had vanished en route to his flat from some promotional event.

There was no answer about the letter. Mycroft could find out, but he had refused, insisting Sherlock leave it in the hands of the French authorities, that Sherlock not get involved – but he was involved, because the timing couldn't be coincidental.

Georges had gotten them to Paris – or at least his name had – and Georges had vanished almost immediately after they'd left.

The detective who had flown over to interview them certainly hadn't missed that connection, but persistent questioning – Sherlock's persistence, not the French officer's – hadn't paid off, and without any actual responses or information, nothing he could deduce did more than generate more questions.

It hadn't helped that Lestrade had been there, putting the brakes on every time Sherlock had been getting somewhere.

But John – John was on his side. In the absence of any official information, or permission to leave the country, there were still ways of getting what he needed. Mycroft's authority didn't extend to inside the flat – John was very clear about that, had been from the beginning. A quick but thorough sweep had prevented Mycroft from listening, and it had been John who had suggested hacking the gens d'armes.

It had taken longer than Sherlock would have liked, longer than it would have with the Met, but the system was new to him. Different. Still, there were back ways and hidden entrances, and he was an expert in those.

Nine months playing dead, moving like a ghost through the world, had sharpened more than just his physical ability to go undetected.

The search into the gens d'armes' system left him not much wiser than he had been before he'd accessed all their information. There was no crime scene – the hired vehicle Georges had been using had vanished, along with its driver. Some very unlucky junior officer was now tasked with scouring traffic cameras, trying to catch one car in a city of millions, but without knowing the route, the possibilities were almost endless.

Without a crime scene, there were no forensics, no clues. Nothing.

The driver's agency had been forthcoming at least, although that too had led nowhere. Three years employment with that agency, impeccable credentials, clean record. Georges had used this particular driver before, so no reason for him to be suspicious.

That would make it easier, of course.

Presuming the driver had been involved, and not himself a victim of a carjacking, a body not yet discovered.

There were too many variables – the elated feeling that normally drove Sherlock stalled by the fact that nothing could be tied together. There was nowhere to start, aside from the scant information they already had, which was nearly as good as nothing.

It had to be Georges himself. There had to be something in his past, some overlooked detail that would mark him out as a target.

Had Sherlock been in France, he could have chased down these fragile leads, spoken to people, picked up on all the poorly concealed hints and tells that were better than lighted signs would have been. He could have found a hidden trail and followed it through the city's streets and alleys and hidden places.

But here– he snarled, snapping the computer shut, startling John.

"He can't just be gone!"

John's eyes widened slightly, lips parting to voice a reply; Sherlock held up a hand quickly, forestalling whatever the doctor was going to say.

There was always a trail.

Always.

Except when there wasn't.

He narrowed his eyes, gaze skimming over the memory of a sweeping landscape of hills and rolling meadows, rocky outcrops against a pristine sky.

They had just been gone. From London to Wales, one moment to the next.

Sherlock opened the laptop again, working furiously, aware (as he always was) of John's gaze on him, silently questioning.

"Air traffic," Sherlock said.

"What?"

"We were taken from here to Wales by helicopter, John, but there had to be some record of it. A flight plan logged – can't fly over the city without someone knowing where you are and where you're going."

"But– wouldn't that be a bit suspicious? 'Oh we're just flying to northern Wales in the middle of the night.'"

"They'd have used a different end destination. Somewhere that took them through the area, where they could have flown to afterwards."

"So you think someone flew Alexandre out of Paris? Out of France?"

"I don't know," Sherlock murmured, half distracted from the conversation by the task of hacking into air traffic control in Paris – not a simple feat, and nor would figuring out the myriad flight paths and air craft on those routes.

He had no idea. It was possible. If Georges had been taken from France altogether, finding him would become exponentially more difficult. But there were other ways to get out of the country, no checks traveling between most continental European countries, and ways around the security going through the Channel Tunnel.

Whoever had taken Georges knew what they were doing.

The person who had taken them had known what she was doing.

"But why?" Sherlock demanded, surprised that John started, surprised at the sound of his own voice. He hadn't meant to say it, not out loud, but now he had a sounding board, even if John hated the subject.

"Why what?" the doctor asked.

"Why would she take him, John?"

John was startled again, pulling back the way he always did now at the mention of her – always torn between which woman they were talking about before figuring it out. It was too complicated, all the ridiculous, unnecessary baggage piled on top of them, like a weight he needed to dislodge to think clearly, but one that he couldn't crawl out from underneath.

"You think– you think she did this?"

"She took us," Sherlock said shortly.

"Yeah, but–"

"And the symbols in the tunnels, John! That paint was fresh – within a day or two of us being down there. Someone knew we'd find it. Someone also knew we'd find him."

"But why?" John asked, echoing Sherlock's question.

The detective pushed himself to his feet, confined by the length of the room, the objects that filled their home suddenly obstacles in his way, hemming him in. Baker Street, London – they were never meant to be prisons, but he was trapped here, as surely as he had been in Wales – more so because Mycroft was keeping him here, not trying to get him out, but he needed to get out, to be where he'd just been, he needed access, contacts he didn't even have in the Paris police force and–

"Deep breath! Hold it!"

The command rooted Sherlock, his body obeying without any input from his mind. Part of him was alarmed at how well it worked, how readily he responded to John's military voice, the tiny piece of resentment swallowed by the ability to refocus, and by the fact that he knew John would never do this to him in public, never let his weaknesses show.

"Good. Let it out. Slowly."

Piercing blue eyes watched him intently until John was satisfied that Sherlock was back on track, but the tension didn't leave his muscles, stiffening his shoulders, and Sherlock knew his partner would pay for that later.

It could wait.

It would have to.

They were already running out of time.

"There was nothing in the novel," John said. Sherlock nodded, mechanically. He'd read it. He'd made John read it. A tenuous hope that the story line would have touched on something familiar, perhaps even reflect Sarraf and Sir Richard's deaths, that he could make a direct link to something George knew about that he shouldn't have.

Georges had friends in the gens d'armes. It could have been something from one of their cases.

As far as he could tell, it wasn't. Maybe small details here and there, but nothing that should get a man abducted.

Vaguely, Sherlock wondered if John would have enjoyed the book under normal circumstances.

He hoped so.

There were too many places to start. None of them stood out as promising, or even likely.

Everything he had built here – and rebuilt since returning – seemed useless. He understood London, how it breathed, how it moved, how to turn its spies and markers and keepers to his own needs.

None of that mattered now.

He was in the wrong place, knew the wrong people.

Sherlock paused, aware of John watching him, careful and evaluating. Something nudged the edge of his mind, something wrong about this isolated, helpless feeling.

It was imposed. Artificial. He didn't know anyone in the gens d'armes but not for nothing had he developed all those contacts in the Met, hammering the important ones back into shape after a nine-month absence.

Mycroft was keeping him trapped here, in a place that was never meant to be a trap, but there was no reason it had to be. Physically, perhaps. But there were ways around it, and if he couldn't go to the information, he would force the information to come to him.

No one else was going to solve this.

It might be a ploy, a dangerous dance, and Sherlock was aware that he was being pulled into it, but stepping back wasn't an option. Not for himself – this game, he would have walked away from, much to John's surprise, and probably much to John's relief, but there wasn't a body, whose fate was already sealed.

There was a man, with the misfortune of having been roped into something he was not part of.

She owed him. She owed him for John, for those three interminable days in Wales knowing there might not be any more John, and now she owed him for this.

"Get your things," Sherlock said, registering the flash of surprise in John's blue eyes, the way he moved for his wallet and keys almost immediately, any questions unvoiced. "We're going out."