The flat was chilly, lit only in the diluted red and green of Christmas lights. Sherlock must have turned the heating down before heading off to… wherever he was. It was likely Sherlock had texted to tell him, but John had turned off his phone.

He didn't bother to shut the door, didn't bother to hang up his coat, crossed the room to sink heavily into his chair. He sat still for a few minutes, got up, got something from the bedroom, sat down again. Waited.

He was still sitting there, staring at the tree, when Sherlock whirled in through the door, coming in halfway through a sentence that trailed and billowed behind him with his coat, flitting into the kitchen and out again, into the bedroom and out again, lights turning on around him, his voice a steady stream of chatter. He kept talking, spinning off in new directions as his mind switched from high speed track to high speed track, asking questions that he answered himself half a breath later, nattering about details that sailed right past, over and around John.

The detective hung his coat on the back of the door, headed for the kitchen again. In a single breath, he managed to ask if John had eaten, conclude a commentary on the state of the transportation industry, and decry his brother's latest cases as "transparent and futile attempts to distract me from real mysteries".

John sat through it all, staring at the tree.

"And of course these sorts of widespread delays could be orchestrated, but I fail to see to what purposes unless sociological research has just received significant increases in funding– and the results would be interesting, perhaps if we really could manage to understand mass hysteria– oh, the possibilities, John, think of the possibilities! Do you suppose some sort of situation could be established in which–"

Sherlock stopped abruptly and John felt himself react slightly – a slight twitch in the muscles around his eyes, a little stronger than a blink – at the sudden silence.

"John," Sherlock said and the tone of his voice had changed entirely. The manic energy had gone; he was no longer monologuing and using John as a sounding board. John felt the whole weight of the detective's genius suddenly focused solely on him.

He stared at the tree.

"John." Sherlock didn't ask if something had happened and John could almost hear him running through a list of possibilities and eliminating the most obviously incorrect ones before narrowing in on the probable choices. John saw Sherlock step toward him out the corner of his eye, but kept his attention on the tree, on the muted red and green lights. Long, cool fingers wrapped over his, pulling his fist open gently, dislodging the dog tags that John was clutching.

He let his gaze flicker up for a moment and saw the litany of names behind Sherlock's eyes, saw each one of them being dismissed.

"Do you know why we went to Afghanistan?" he asked, his eyes dropping back to the tree.

He felt the hesitation against his skin before Sherlock drew the dog tags away. John let them go without comment.

"Which of the many reasons would you like to me give as an answer?" Sherlock asked in reply. John's lips twitched but there was no humour in it.

"Do you feel safe, Sherlock?" John asked softly.

"If I feel safe then I know I'm doing something wrong," the detective replied and John felt his lips curl again, the expression vanishing as soon as it had appeared. He sighed and heard the faint clink as Sherlock tucked the dog tags into a pocket. The detective moved away to close the door, then came back and settled in his chair.

"Do you understand what it's like to live every day knowing you could be blown up or shot?"

"Yes," Sherlock said simply.

"No you don't," John contradicted softly. He heard Sherlock shift, then quiet inhalation that came before speaking, but he cut his husband off. "You don't, not really. You expect it – but with you, when it happens, it's because someone is playing a game with you. With you. You're not a game piece, you're the opponent. Moriarty, even Mycroft..."

He shook head, his gaze never leaving the tree. "When I was in Afghanistan... it's different when you're a soldier. You have training, you have resources if you want them. I didn't have to try and imagine what it was like for the people who lived there. I saw it all the time. Constant stress. Living in a warzone. Every time they left their homes, having to wonder if they'd get blown up. Hell, having to wonder that just being at home."

"The human mind is remarkably adaptable, John."

"Yes," John said. He knew that. "And no."

There was a silence that stretched between them that John didn't try to fill. He watched the lights on the tree. A few of them here and there were burnt out, needed to be replaced. Sherlock would probably have been able to tell him precisely how many.

There were a handful of wrapped gifts under the tree already, too. And not just his. Sherlock's wrapping jobs were always precise and careful. John had initially expected haphazardness from his husband, but he'd been wrong.

"John, what happened?" Sherlock finally asked. It struck John as the oddest question – surely Sherlock knew? That was what he did.

The doctor raised his eyes to meet the detective's and saw that there were still some uncertainties there. He could have figured it out, deduced it all down to the answer, but he was waiting for John to explain. Irrationally, he found this both endearing and stupid.

"Do you know what RIRA is?"

"The Real Irish Republican Army," Sherlock replied promptly. John was surprised, then he wasn't. "A splinter branch of the IRA."

"Yep," John replied. He let his eyes drop away. There was another long moment of silence and John felt a sudden cold weight settle in his stomach. "You knew," he said, raising his eyes, narrowing them as he met Sherlock's gaze. "You knew, didn't you, Sherlock?"

"I suspected," Sherlock corrected.

"You 'suspected'," John repeated in a murmur, then stared at him in disbelief, anger snapping. "Why the bloody hell didn't you tell me! He's a fucking terrorist and you– you just let me–"

"Because it was one of several options," Sherlock interjected, a sharp hint to his voice that made John shut his mouth abruptly, pursing his lips.

"What?"

"I told you I could have formulated several hypotheses about him."

"And you did," John said flatly.

"Of course I did."

"How many?" he snarled.

"Five."

"Five? Five! You let me run around stupidly while you had five actual theories about him that might have helped – and I wasted my time on a bloody fucking terrorist while–"

"No," Sherlock said and John stopped short again.

"No?"

"Five hypotheses, not theories, John. Based on incomplete information garnered from a man with no memory whose physical appearance could tell us very little given how badly injured he is."

John stared, a numb sensation settling over him.

"Let's have them, then."

Sherlock sighed and gave him a pointed look, but John held his gaze until he saw the faint flicker of expression that meant the detective was relenting for him.

"Given your initial assessment of the bullet wound to his leg, my immediate deductions were: police officer, criminal, military, or paramilitary."

"That's four things," John said.

"I can further refine police officer into two categories: undercover or not. I was able to dismiss police – either condition – or criminal given the fact that his fingerprints did not turn up a match in the system beyond the possible match to the Connolly case twelve years ago. A police officer would have been printed and any search for an undercover officer would have immediately alerted the proper people and Donovan would have found out who he was within fairly short order. It's possible that he was a criminal who simply wasn't apprehended, but if he were, and if he were shot while working, then his arrest is far more probable. Impossible to get treatment for a gunshot injury at a hospital without the police knowing – of course this assumes that he didn't have access to private no-questions-asked healthcare. Given the state of his hands, that would be unlikely. As you said, works with his hands, probably a manual labourer, so not the type of person to be able to afford such discreet care.

"His hands also eliminated the possibility of him being a police officer – why would he show signs of such physical labour? But perhaps he was shot while on duty and retired early and changed professions. That doesn't solve the problem of why he didn't turn up in the police system. Of course, if he were from another country – Ireland, for example – his identity isn't likely to be on file with the Met and other British police forces.

"So, unlikely to be a cop. Donovan doesn't have access to the military fingerprint database, so he could have been in the army. Bullet wound, works with his hands – you've told me there are any number of professions within the armed services in which one could work with his hands on a regular basis. It would explain why he had the injury and the physical evidence of his work that he does.

"Although it wouldn't explain why Mycroft couldn't find him in the military databases."

"You think Mycroft ran his fingerprints?" John interjected.

"Of course he did. He got you the information, didn't he? He's not the type to simply let something like that pass through his hands without at least some cursory investigation, John. Information is power. If he could find out who Doe was, it might be useful. It would be easier for him to access the British army rather than any other country, although he might have been working on that. It simply would have taken more time. If Doe was in the British army, we would have known about it by now.

"But what else is military and requires any number of skills to accomplish its objectives? Paramilitary – terrorist – organizations. The IRA has a number of splinter groups. These do not have databases with files on each member, so no fingerprints there. And if he were a member of one of these branches, he'd have to have a regular job as well – he'd need an income and a cover. Construction is a good choice – he may not be an engineer, but he'd have a solid working knowledge of the strengths and weaknesses of building structures, which would be useful for planting explosives."

John opened his mouth to say something else but Sherlock shook his head and kept talking.

"Of course, there is a sixth possibility that he's nothing more than a man with a physical job who happened to have been shot at some point – wrong place, wrong time – and was recently attacked for reasons unknown. Personal? Random? Hard to say. Perhaps he's just unlucky. And it could be that any of those deductions were wrong because all we had was a beaten man with no memory and calluses on his hands and an old bullet wound to his leg. Hunting accident? Perhaps he does wood working as a hobby?"

"But you didn't believe that."

"I thought British military, Irish police, or IRA the three most likely choices, yes," Sherlock agreed.

"And you couldn't think to tell me that?" John snapped.

"Which one would you have chosen?" Sherlock sighed.

"What?"

"Which option would you have chosen, John? Would you have assumed the best of him or the worst?"

John stared, then rubbed his hands together and looked away.

"Because you are who you are, you would have assumed the best – that he was a former soldier or a former police officer."

"And I'd have been wrong!" John retorted, glancing back.

"And you'd have been wrong," Sherlock agreed with a nod. "But you would have picked either of those options and you would have carried investigating regardless."

"If I'd thought for half a second–"

"You would have stopped? No." Sherlock leaned forward, fixing his bright grey eyes on the doctor. "You would have told yourself there was a possibility you were wrong and you'd have continued trying to help him because he may not have been guilty."

John sat back in his chair, turning his eyes away again.

"Well, he is."

"I assume he's been arrested?" Sherlock asked.

"No, actually," John said and saw Sherlock turn his head slightly with that half-puzzled, half-suspicious look he got when he was wrong and surprised by the revelation. "An inspector from the Gardaì in Dublin came over – she saw him on the telly, too, bit later than we did, apparently – but nope, not arrested."

"A suspected terrorist then? But no, they'd have arrested him for that. Does his medical condition preclude arrest?"

"Nope." John waited, watching Sherlock watching him. "He's paid his time, apparently. Informant. Got found out though, so they had to move him here, give him a different name. Oh yeah, that's right. His name is John, Sherlock. He was right about that – Liam – Liam Walker, by the way – was– is– whatever – his assumed name. John Riley. From Dublin. Specializes in bombing, apparently. Good fit – you were right: he'd have to work with his hands."

"An informant," Sherlock said, arching an eyebrow, and John sighed sharply.

"Yeah."

"So he changed his mind."

"What?" John demanded, feeling a flash of irritation when Sherlock sighed.

"You're angry at him because he was a terrorist – precisely the same kind of problem you were fighting against in Afghanistan. But he changed his mind. Oh, granted, he was a terrorist. And then he decided this was objectionable and began assisting the police, a decision which led to him being removed from his home, his own identity, and moved to England. But you're angry with him."

"Of course I'm angry with him!" John snapped. "He was a bloody terrorist! He blew people up in the name of disliking his government! Or our government, whichever. Doesn't bloody matter."

"So not at all like our military does in other countries."

"That's different!" John retorted, pushing himself to his feet.

"Is it?"

"Yes! Because–"

"Because it's sanctioned? Because the weight of the government behind the force lends it legitimacy? Perhaps it's only a matter of perspective."

"Oh, yes, thanks for that, Sherlock! I'm really glad I can count on your support! So nice to know that the person I'm married to thinks that–"

"I don't think that," Sherlock interjected calmly. "I'm suggesting he might have."

"Blowing people up is not a solution!"

"I never said it was."

John stopped and sucked in a deep breath, raking his hands through his hair.

"And, evidently, he came to agree with you," his husband pointed out.

"What?" John snapped.

"You cannot be angry at him for being a terrorist and then refuse to acknowledge that his opinions on the matter changed. At great personal risk to himself, I might add. That can't be a decision made lightly."

John circled behind his chair and gripped the cushions, leaning forward.

"And now you're also angry that he betrayed the trust of his fellow RIRA members– Wait, no. You're angry he betrayed your trust."

John felt his fingers tighten involuntarily on the upholstery and set his jaw, meeting Sherlock's eyes squarely.

"I was wasting my time on a bloody terrorist–"

"No."

"What?"

"No, you weren't. You were trying to help an assault victim, John. Stop for a moment and listen. No, don't just stare at me waiting for the next opportunity to say something, really listen to me, John. The man you're helping is not a terrorist."

"He's–"

"There was a man with his name and body who was a terrorist, yes, but not with his mind. He is not the same person. You're a doctor, I know you understand this. How much does he remember even now? Still very little, I'd wager, and likely none of it very significant or personal. Over forty years of life and memories that would – if you could distil them into liquid form – probably fit into a coffee mug. He is not John Riley, nor is he Liam Walker. He can keep either name and he retains the genetics, but even if someone could provide him with descriptions of every event in his life, they still wouldn't be his memories. All of those experiences which built him, they're not there right now. They may come back – but even if they all do, there's no guarantee that he will view them the same way he used to. He is, quite simply, not the same person."

John stared across the small space and Sherlock met his gaze with a level expression.

"He did not deceive you, he did not lie to you. In fact, I'm certain he told you nothing but the truth. He had no reason not to. You've befriended him, John – in fact, you're the only person who is friends with the man he is right now."

John bit his lower lip to withhold a sigh and shook his head. He drew away from his chair, raking his hands through his hair again.

"People don't change," John muttered.

"Don't they?" Sherlock replied. The doctor glared over his shoulder but Sherlock was still watching him with equanimity. He sighed, running a hand over his face, annoyed that Sherlock had taken that position. The detective loved to point out how people were creatures of habit, but John knew that wasn't always the case.

"Regardless of who he was, it does not make him responsible for Patrick Connolly's murder. Will you judge him guilty of that because you know something you dislike about him? And he is still the victim in a severe assault. Unless I'm very much mistaken, that level of injury would be impossible to inflict on one's self."

"So what should I do, Sherlock?" John snapped.

"I'm not telling you to do anything," his husband replied. "I'm giving you perspective."

"Perspective," John muttered.

"Continue investigating or don't, John," Sherlock replied with a light shrug. "I'm only suggesting you make the decision for legitimate reasons and not because you feel betrayed by a man who owes you nothing who happens to have a past you don't like."

A/N: Over on tumblr, buckledrawsmanga did an amazing piece for this story: tinyurl 89mnhk7 which took my breath away.