221b had seemed too obvious a place to look, but John had started there all the same. Predictably there was no sign of Sherlock. but John had found himself peering into the wardrobes and under the beds, climbing the rickety ladder that led up to the attic storage space and even asking Mrs Hudson to open up 221C, just in case.

Greg, meanwhile, still convinced that Sherlock had gone to find drugs, had called in reinforcements to do a tour of Sherlock's known bolt-holes and local squats, starting with the one that John had found Sherlock in that fateful morning, but of Sherlock Holmes there was no sign, and even Bill Wiggins seemed to have disappeared. John couldn't help but wonder if Bill hadn't been involved in Sherlocks escape - he would have needed an accomplice after all.

The list of bolt-holes given to Greg by Mycroft had yielded no evidence of Sherlock either, and Molly's flat, when John had sent her home to look for him there, had also proved empty.

Because Sherlock wasn't hiding, John had suspected that from the beginning. He had left the hospital for a reason, and John was fairly sure that he knew what that reason was. He didn't buy Greg's explanation of him leaving to score drugs. That awkward, addicted teenager that Greg remembered had been a lifetime ago. Sherlock had been hooked up to a morphine infusion in hospital, he'd had the drugs on tap, and as he hadn't shown any signs of withdrawal from cocaine or ketamine, it seemed unlikely that he would have left hospital to seek those. Besides, if Sherlock could manage to break out of hospital without being detected, then having drugs brought into him wouldn't have been an issue.

There was only one thing that would have made Sherlock leave his hospital bed - a case; a mystery; the need to find answers, and to solve a puzzle, John knew him well enough for that. He'd gone after the shooter, John was sure of it. But why?

Even Mary had drawn a blank on that one, although she had volunteered to go and talk to a few people for him - Stanford, Andersen, Angelo, anyone who Sherlock might have talked to, who might know where he could have gone. Looking for Sherlock in London was like trying to find a needle in a haystack - worse, it was like trying to find a needle who knew every inch of that haystack, who knew how to disappear into it, like a ghost.

In desperation, John had found himself walking the streets, going to familiar places, trying to think like Sherlock, to find anyone who might know where he had gone. Sherlock had always seemed able to find one of his Homeless Network without any perceptible effort. It took John a good half an hour to finally find someone that he recognised, a girl who claimed to be nineteen but who John had always suspected was much younger, settling down for the night by the skatepark on the Southbank that had just been saved from redevelopment. He had asked her if she had seen Sherlock, trying to slip her a twenty pound note, in a poor imitation of Sherlock's nonchalant style, but she had just shaken her head, and pushed the money away.

'Look he's hurt, I need to find him.'

She shrugged. 'Sometimes people need to disappear,' she said. 'And it's not up to us to grass them up.'

'So you do know where he is?'

'No, I told you. Haven't seen him.'

'Could you ask about a bit, maybe? I'll reward anyone who can tell me where he is.'

She shook her head again. 'You're not listening to me,' she said. 'Nobody's seen him. Nobody is going to have seen him until he wants to be found. Until then I'd leave him be.'

It had reminded John uncomfortably of his conversation with Bill Wiggins a few days previously, but something jarred. 'Until he wants to be found.' What if he did want to be found? What if he was leaving John clues, starting with the dummy in the hospital bed. What if this was a treasure hunt after all?

He had phoned Greg, who was running out of ideas as fast as he was, and suggested that they re-convene at 221b. If they wanted to find Sherlock Holmes, then they were going to have to think like Sherlock Holmes.

...

'He knew who shot him,' John said, pacing the room in an unconscious imitation of Sherlock. 'The bullet wound was here,' he tapped the front of his chest. 'So he was facing whoever it was.'

'So why not tell us?' Lestrade asked. 'Because he's tracking them down himself?'

John's original theory, but it seemed too simple somehow. Why would Sherlock be after the shooter? Not for revenge, it wasn't his style. Sherlock never wanted revenge, he wanted answers, and if he had answers then he would have told them what they were - he never could resist showing off. No, if he was going after the shooter then there was only one possible explanation for that.

'Or protecting them,' he said slowly. What was it Sherlock said? 'When you have ruled out the impossible then what remains, however improbable, must be the truth'. Sherlock hadn't told them who the shooter was because he knew them. Because he was protecting them. However improbable that might be, it was the only possible explanation.

'Protecting the shooter? Why?' Lestrade asked, echoing John's own thought procesess.

'Well, protecting someone, then,' John said, thinking out loud now. 'But why would he care? He's Sherlock. Who would he bother protecting?'

He sat down in the chair without thinking, thinking how friendly it felt, how familiar, then looked down at it.

His chair, back in it's original place. The chair that Sherlock had moved out because it had allegedly blocked his view of the kitchen. The chair that he had moved when he had replaced John with Janine, or maybe with Bill Wiggins. The chair that he had moved to prove to John that he had moved on. Back where it had always been - opposite Sherlock's chair, ready for late night conversations. Ready for him to sit back down in it and - what? Another clue? It had to be.

'Call me if you hear anything. Don't hold out on me, John,' Lestrade was saying, but John barely heard him, still trying to work out the mystery of the chair. When had Sherlock moved it back in? It hadnt been there when he'd come to search 221b for drugs, he was sure of it. Had it been there earlier that evening? He was frustrated to realise that he couldn't remember.

'Call me, okay?' Lestrade was saying.

'Yeah. Yeah, right,' John replied, trying to work out what it meant. The chair, the dummy, the search for the shooter. Clues, so many clues. The answers had to be there somewhere. In this room, in this flat. He stroked the arms of the chair, trying to find answers in the fabric, in the familiarity. He knew Sherlock, even after all those years that he was away. Knew him better than anyone, better even than his own family. That was what Sherlock was relying on, he was sure of it. He was relying on him to work it out.

Distantly he was aware of Mrs Hudson saying goodbye to Lestrade, he was impatient for him to leave, because he had worked out something else. Sherlock didn't want Greg to know. The clues had been planted for John, only for John. 'Who would he bother protecting?' John had never so desperately wanted to be wrong over the answer that he couldn't help but form to that question.

'John? Need a cuppa?' Mrs Hudson was asking. A nice cup of tea - her solution to everything. It reminded him of his first visit to 221b, of the cabbie, of Sherlock's disappearance to find him, of him banking then on John picking up the clues, that he would find him in time to save him.

If Sherlock was relying on him to find him again then he might be about to be severely disappointed. And yet there was this undeniable clue. The chair. The clue was the chair. But what was Sherlock trying to tell him this time?

'Mrs Hudson?' he said, half turning towards her, wondering if she would work better or worse than the skull that Sherlock had used to favour talking to in John's absence. 'Why does Sherlock think that I'll be moving back in here?' Because that was what it meant, wasn't it? The chair, his chair, back in its place. That was exactly what it meant.

'Oh, yes, he's put your chair back again, hasn't he? That's nice! Looks much better.'

Look - of course, that was it. Sherlock knew that he would come in here when he failed to find him, knew that he would sit down in his chair, knew that he would look - first towards the kitchen where Mrs H would of course be making the ubiquitous cup of tea, and thenvthat he would turn his gaze the other way. To the side table on his right, and on that was, was...

John felt sick. Transfixed by the object on it. Unable to look away. Unwilling to believe what Sherlock was trying to tell him.

The perfume bottle. Mary's perfume bottle. The duty-free bottle that she had got when they were returning from their honeymoon in Barabados. He recognised it from the slight chip in the bottom right hand corner where she had dropped it on the tiles of the bathroom floor when she was unpacking.

Mary's perfume.

The perfume that Sherlock had detected in Magnussen's office.

The perfume that had belonged to the shooter.

Memories flooded into his head, one after another,. Mary looking tired and drawn the morning after the shooting, vomiting when he told her of the extent of Sherlock's injuries.

Mary refusing to go to see Sherlock with him after that initial visit.

Sherlock saying Mary's name as he woke up from his sedation.

Sherlock refusing to tell anyone who had shot him.

His own voice again, asking Lestrade who Sherlock would want to protect.

Mrs Hudson was talking, but he couldn't hear her, the words made no sense. He felt oddly distant and light-headed. He forced himself to look away from the bottle towards the window for a moment, to take a few deep breaths, to try to still the ringing in his ears. And then he realised that the ringing was real that it was coming from the room, from his phone.

And then Mrs Hudson was holding his phone out towards him, and he was taking it and blindly stabbing at the screen to pick up the call, unable to speak, unable to acknowledge the voice on the other end.

'I'm sorry, John,' the voice said. And then he knew that it was true.

This chapter comes with thanks to Ariane DeVere for her excellent transcripts.