John followed the tempest out into the hall, ignoring the framed picture Sherlock had dropped on the plush carpet, and back through the flat, not particularly hurrying, but keeping up fairly well because he really did want to see how this played out. Sherlock was yelling his brother's name in a tone John had never heard before – he had never actually seen Sherlock this blazingly angry. He'd seen him angry plenty of times, especially with Mycroft, especially over the last year and a half, but nothing like this.

John didn't blame him. What was Mycroft trying to pull?

Mycroft came back into the flat, standing in the door, a rare puzzled look on his features. Sherlock pointed past him at the other agent who was waiting outside in the small lobby, framed by the closed lift doors behind him.

"You! Out! Now!" Sherlock barked.

The other man looked at Mycroft, who gave a nod in return, then stepped fully inside, shutting the door. He moved into the livingroom, where Sherlock had stopped, his face bright, eyes looking a paler grey than normal in the dim light of an overcast day that was coming in from the windows. He kept back from Mycroft, but still towered above him. John had initially thought they looked fairly unalike, but the more he got to know them, the more he saw the resemblances. It would explain a lot about David's eye colour – although neither Sherlock nor Mycroft had blue in their eyes, the grey colour mixed into David's eyes was responsive to the colours around him. John recalled the photo in the file that showed him with greyer eyes, the same pale hue as Mycroft and Sherlock. As his father and uncle, apparently.

"You don't know who his father is?" Sherlock hissed, jaw clenched, eyes livid. "Really, Mycroft? On something like this, you would withhold that information?"

Mycroft looked from Sherlock to John, appearing a touch surprised, as if trying to pin down which of them had figured it out.

"David doesn't know," Mycroft said coolly. "I have nothing to do with him."

"You're his bloody father!" Sherlock retorted, throwing his hands up in frustration, looking to the ceiling momentarily as if it could give him some answers, or at least be more reasonable than his brother. "Your own bloody son goes missing and you still think this is a game you need to play? To do what? Protect yourself? You cannot tell me that you haven't considered this has something to do with you and not Angela MacTaggart! How in the bloody hell am I to provide you with help when you won't give me the information I need to assist you?"

John could tell Sherlock was on the verge of calling it quits, of going home. He wouldn't have blamed him a bit had he made this choice. He had a more than valid point; how was he supposed to accomplish anything when missing a significant portion of the facts?

It complicated matters a lot, John considered, that both of David's parents were agents for – whoever the hell they worked for.

What a thing to pin on a child, he thought. Instead of one parent's host of enemies, he had two parents' worth. And he was only ten. It was almost a miracle, actually, that he'd made it this far without running into this kind of serious trouble.

But it would make it so much more difficult to figure out why he'd been taken. How many enemies did Mycroft introduce into the mix? How far back would they have to look? Would following up on Mycroft's contribution only distract them from Angela's? She may still be the real target.

Mycroft gave a sigh and a long-suffering look.

"Of course I have been checking leads pertaining to myself," he said. "Discreetly. I don't want to alert anyone who may be watching me regarding this that I'm considering it, if only for David's sake. If it has nothing to do with me, then whoever has him would only find more power against Angela and more information to use as leverage. I do want to avoid that.

"As for David, yes, I am his father, only in the strictest of senses. Sherlock, I've only met the boy twice. As far as he's concerned, I am unimportant, someone his mother used to work with and that's all."

John raised his eyebrows. Mycroft turned his eyes to him and nodded briefly.

"This had nothing to do with me," he continued. "Angela wanted to have a child. Given her level of intelligence and aptitude and mine, and the fact that we both have healthy genetic backgrounds, we were an ideal match. You can see that quite clearly from David's school records and the reports on his behaviour and personality. She asked me to keep this to myself, and I certainly had no interest in being a parent. I was involved genetically and that was all, Sherlock. He's not my son in any sense but that."

"And how many people knew about this?" Sherlock asked in a quiet, cool tone. John wasn't fooled for a second that his husband had calmed down; his eyes were still flashing and he was still holding himself too still for a composed Sherlock, who was much freer and more fluid with his movements.

"If you're asking whether there were doctors involved, the answer is no. We did this the old-fashioned way. Oh, don't look so surprised; Angela and I had been lovers earlier on, when we were younger."

Mycroft said this in a way that told John there hadn't been much of a romantic liaison there, only a physical one. Although this didn't surprise him – because it was Mycroft, after all, not a man to put any sort of emotional desires ahead of his professional goals – John thought it was a bit cold. He had no idea what Angela MacTaggart had thought of this arrangement, but if she was anything like Mycroft, and John suspected she was, then it had probably suited her just fine. Still, it seemed an unpleasant way to live. He himself could not imagine it – he'd been at least interested in all of his former partners as people, if not actually in love with them. But then, Sherlock had had the same impersonal arrangement in university with Charles that Mycroft had apparently had with Angela. Perhaps the anomaly here was their own marriage, at least in terms of how the Holmes brothers approached relationships. He didn't know.

"Up until now, Angela and I were the only ones who knew about it," Mycroft said. "No one else."

"Best not to count on that," Sherlock snapped back. "If this is about you, then someone else has figured it out. It didn't take John long, after all."

"John spends quite a bit of time looking at you," Mycroft replied. "And yes, David looks somewhat like you, because you look like Mummy, and so does David. If you had passed David on the street, neither one of you would have given him a second glance. I agree the resemblance is there, but it's not so noticeable as to be striking."

"Perhaps not," Sherlock said. "But whoever figured this out would not have simply passed him by on the street. Do you not ask yourself who's watching you?"

"All the time," Mycroft said simply. "Particularly since last February. I warn you, Sherlock, if it's one of your Interpol friends who's taken him, there will be consequences."

"If Interpol wanted something from you, there would be much better way to attain it, Mycroft. Whatever enemies you've made there through me would not stoop to kidnapping a child – sorry, your son – to get what they wanted."

"Are you certain about that?" Mycroft asked.

Privately, John wasn't so sure. It didn't feel right that this involved them somehow, and he agreed with Sherlock that there were much better ways for Interpol to get whatever they wanted from Mycroft, because they could go through Sherlock for access to him. But, when it came down to it, neither of them really knew that much about Sam Waters – Yves Bessette – nor what he was capable of. They'd befriended a Metro police constable, not the Interpol agent behind that constable. Neither of them knew where he was now, although they occasionally got letters and cards from across Europe and once from Australia, nor did they know what his agenda was, nor his assignments.

Still, John considered it unlikely that Sam would contract or condone the abduction of a child, given what had happened to him at Moriarty's hands.

"Certain enough to move them quite far down on my list of suspects," Sherlock agreed and John was glad that his husband wasn't ascribing blind faith to Sam and all of Interpol.

It was even conceivable, John realized, that Mycroft had other Interpol enemies who didn't know anything about Sam Waters and wanted something from the elder Holmes brother.

Thinking about all of this spy nonsense made his head hurt. He almost wished for the simplicity of Afghanistan, when, if someone wanted to get at him, they'd just shoot.

"And what list is that?" Mycroft said.

"I don't know, do I?" Sherlock retorted. "Seeing as how a wealth of valuable information has been kept from me! Would you like me to also work with my eyes closed, Mycroft? Perhaps you could arrange for all of the files to be written Sanskrit as well, to make it more complicated."

"Stop being dramatic, Sherlock," Mycroft said wearily.

"Says the man who dragged me across two countries to find a missing boy who just so happens to be his son without informing me of this or of any possible connections with his own cases. If you wish me to continue working on this, you will immediately give me access to any other information you consider pertinent. The next time I find out you're lying, John and I are leaving, regardless of whether or not I've made any progress. How can you expect me to get anything done without knowing about David's full history?"

"If it has nothing to do with me, then you didn't need to know," Mycroft replied.

"And I cannot rule that out without knowing, can I?" Sherlock snapped. "Really, you may as well write the whole affair off right now."

At this, Mycroft's nostrils flared.

"Uninvolved as I may be, I do not wish to see David harmed," he said quietly, his voice bordering on dangerous. "What I said earlier was true: whatever sins his mother committed should not be visited on him. That goes for his father as well. If this is linked to me, then it should have nothing to do with him."

"I'll need access to all your files," Sherlock said, then gave Mycroft a warning look when his brother hesitated for a fraction of a second. "You asked me here because no one else has found anything. If you want me to find anything, I strongly suggest you begin to cooperate now, Mycroft. You've already lost too much time on this. Best not to lose any more."

Mycroft installed them in a suite at the Balmoral Hotel, which irked John, not because it was well appointed, but because it was where he and Sherlock had stayed during their honeymoon. It was annoying that Mycroft knew this, but John supposed he could consider it a mercy that Mycroft hadn't actually booked them into the same room. The suite was larger – John hadn't let Sherlock spend an excessive amount of his money last time (although had he known precisely how much of that money there was, he wouldn't have bothered worrying about it) – and it meant that Sherlock could kick Mycroft into the sitting room after his brother had set them up with a network of computers and had arranged for Angela and David's computers to be delivered to them.

"Don't go anywhere," Sherlock told Mycroft coolly. "And try not to think too hard or be too obtrusive."

Mycroft hadn't commented but had left them in the bedroom, Sherlock installing himself immediately at the desk in front of the computers, his grey eyes blazing, but in a different way now. John felt somewhat discomfited, because the last time he'd seen precisely that look was when Sherlock had been dealing with James Moriarty. He knew some part of Sherlock missed having an opponent like Moriarty, missed the complex games, missed the challenge of someone on his level intellectually. John was thoroughly happy the man was dead – he didn't fancy having people in the world who would strap bombs to bystanders' chests or kidnap and rape police officers. There were still people like that out there, so the fewer the better.

Now Sherlock was being given another complex puzzle, with opponents who were equally, if not more, dangerous than Moriarty. The best John could hope for, he supposed, was that they weren't psychopaths doing this for love of some perverted game, but practical men or women with a specific goal. It was possible that they were dealing with a psychopath with a goal, which was still better than a psychopath just playing around.

He supposed it didn't matter much to David.

Nothing about Sherlock's demeanour seemed to indicate that he was taking this at all personally, this loss of a nephew he didn't even know he'd had. John doubted it had even occurred to him – and how would it have had? He hadn't known for more than an hour that David was related to him, and David's own father had only met him twice. For all practical purposes, they were dealing with a complete stranger. John had no illusions it wouldn't remain that way for Sherlock; he couldn't at all picture Mycroft as a warm, caring parental figure, or even a cool, distant parental figure. With that reality, there was no reason for Sherlock to care, particularly since he didn't get along with his brother.

Sherlock already had a niece to whom he was ridiculously attached – John also knew he wasn't about to divide his attention between Josephine and a boy whom he didn't know and who didn't know him. In a way, John was glad about this, because Sherlock did better when facing only the puzzle, not any sort of personal complications.

John rang down to room service and ordered them some food; he was famished by now, especially since he hadn't eaten on the aeroplane, refusing any attempts Mycroft made at being hospitable. Sherlock had no sense of stopping for food when he was working, so he gave the consulting detective a cup of tea and a plate of biscuits when they arrived, which Sherlock could at least consume without concentrating on it. John sat on the ridiculously comfortable bed and watched Sherlock work, his expression focused so tightly John wouldn't have been surprised if his own presence had been forgotten, his grey eyes intent, snapping across information on the screen.

"What are you doing?" he asked finally. His voice didn't startle Sherlock, but didn't make him move his gaze, either.

"Looking through some of Mycroft's files more obviously than he's been," Sherlock replied.

"Why?" John asked. "Shouldn't you want to keep anyone from being alerted?"

"Precisely the opposite of what I want," Sherlock replied. "It's been three days – if they wanted something from Angela, they'd have been watching activity on her history and contacts, et cetera, which we know Mycroft's people have been digging through. They would have contacted her by now, unless no one has yet stumbled across the people in her past who are behind this. However, if this has to do with Mycroft, which I think is more likely at the moment, then his discreet enquiries might go unnoticed. I want whoever has David to know we're looking. They want me to be looking."

"You specifically?" John asked around a bite of a rather good club sandwich.

"No, anyone," Sherlock replied off handedly. "They want a response."

He kept working while John finished eating then cleared his dishes back onto the tray. John wondered if he should check on his brother-in-law, but then thought better of it. It would only distract Sherlock, and Mycroft could handle himself. He didn't have much sympathy right now – as ever – for Mycroft, but he did have sympathy for this boy who was apparently Mycroft's son.

John found he really, really didn't like this idea. He tried to imagine what he would have thought if he'd found out that Harry had had children. He could only feel glad that she hadn't.

The buzz of Sherlock's phone distracted him and Sherlock's eyes lit up with a triumphant gleam. He fished it from his pocket and unlocked it as John crossed the overly large bedroom to stand next to Sherlock's chair in front of the mess of computers on the polished dark wooden desk.

There was a text message with a photo attached. The photo was of David, eyes closed, skin with a slightly blue tinge, but not because he was lacking oxygen, because of the lighting surrounding him, John could tell. His clothing had the same colouration, even though he was still dressed in the same dark red t-shirt in which he'd last been seen, and the non-descript wall behind him was bluish as well, probably concrete, John thought. Nothing distinctive on it or about it.

David's face was unmarked and he had his hands curled up next to his right cheek, as though he were sleeping, but the point of this pose was to show the handcuffs fitted securely around his wrists. John did a quick assessment, insofar as he was able, and suggested David was drugged, and that the faint marks on his wrists indicated that the handcuffs were not too tight, and fairly well lined against him slicing his skin on them. If they were police cuffs, which Sherlock confirmed they were, or at least police-standard, then they'd been modified enough to keep the boy from injuring himself when he struggled against them.

The text read:

It's about time. Show this to your brother. Have him think hard about this. We'll be in touch again soon.

The number, of course, was blocked and John was willing to bet untraceable. He and Sherlock exchanged a dark gaze before the consulting detective stood and headed for the bedroom door, looking not at all pleased at being right, even in the face of being able to lord it over Mycroft's head. John followed, wondering how this was going to go over.