This story started life as 'the plus one' to Explanations, but it's evolved into something more than that.

It is set immediately after the plane scene in TAB, as will become obvious...

Sherlock Holmes and John Watson were sitting in companionable silence in the living room of 221b Baker Street; each had a pipe of tobacco in their mouth, and there was a fire burning in the hearth. Holmes felt a rare moment of contentment as he watched the flames. Another case solved, and the prospect of more to come. Watson was back where he should be, in his old seat at 221b, and while both of them were well aware that later he would make his excuses and return home to Hampstead, neither of them chose to mention it.

'Sherlock - time to wake up now.'

The voice seemed to come from nowhere. Holmes looked round, but could see no-one, and Watson seemed blissfully unaware of the intrusion.

'Come on, Sherlock, we need you to wake up.'

There it was again - the disembodied voice. Where was it coming from? He stood up, trying to put down his pipe which seemed oddly wedged in his mouth. Uncomfortably wedged, now he came to think about it and located much too far back. It felt as if the stem was being forced down his throat. He coughed, trying to dislodge it, then started to gag, clutching his throat, gasping for breath and frantically signaling at Watson to help him, but Watson remained motionless, staring into the flames as if frozen in time. Holmes staggered towards him, but his legs wouldn't hold him and he fell, not onto the floor but straight through it as his eyes snapped open to...

Lights. Bright lights. Too bright. And voices, talking to him, telling him to breathe out and then with a horrifying rasp, the pipe stem was removed and he could breathe again. Something was placed over his nose and mouth, and he tried to push it away but a hand seized his, stopping him.

'Leave it, Sherlock, it's just an oxygen mask. You're in hospital, you need to lie still.'

John, it was John Watson. The voice was John's, and so was the hand still holding onto his. Curiously he found that he didn't mind the physical contact. He found it rather comforting.

He blinked, trying hard to focus and then tried to sit up, but he felt oddly weak. The hand not restrained by John was tethered somehow, preventing him from moving. Where was he? Was he still on the plane? Had he miscalculated the dose somehow and passed out? He had been in his Mind Palace, projecting himself deliberately back into Victorian times to solve the case of Emilia Ricoletti and solve it he had.

'John -' he tried to say, but his voice came out as a croak.

'Don't try to talk,' John said to him. 'You've been intubated. Your throat is going to be pretty sore for a day or two. Just lie still.'

He blinked again, trying desperately to focus on John. 'What -' he managed.

'You're in hospital, Sherlock. In Intensive Care. You overdosed, nearly stopped breathing. Bloody good job I had my visit bag in the boot of the car and could give you some naloxone. It didn't wake you up, but at least it kept you breathing until the ambulance got there.'

Overdosed? He hadn't done that in a very long time. Not since before he'd met John in fact. He was always so carefully with doses and timings, but there had been an urgency this time that had made him careless. That together with the reduction in his tolerance caused by the enforced abstinence for his week-long stay in custody must have been enough to tip him over the edge.

He looked at John who seemed to have just realised that he was still holding Sherlock's hand and let it go.

'What time is it?' he asked, his voice still croaky.

John looked at his watch, 'Three twenty-five in the afternoon' he said.

Three twenty-five. Good. He hadn't lost too much time then. The plane had taken off at 10.15am, he had only lost a few hours.

'You didn't ask what day it was,' John said, watching his expression. 'It's Friday. You've been unconscious for over a day.'

'Moriarty!' Sherlock croaks, trying to sit up again, only to be pushed back by John.

'Mycroft is dealing with it. It's just a computer virus anyway, that's all. A complex hack. He's tracking it down, but it looks as if it could all be a scam. No signs of anything sinister that he can find.'

'Emilia Ricoletti -'

'Why do you keep going on about her? It's not the same case, Sherlock. You proved that Moriarty really was dead, good for you. Yes, it's possible that somebody is taking on his persona, and trying to reactivate his network - the bits that you left behind anyway. Or this could just be a copycat trying to cash in on his fame. Either way, it got you a pardon and you're off the case.'

Sherlock pulled the oxygen mask away from his face before John could stop him. 'How can I be off the case?' he asked.

John grimaced. 'Mycroft is pretty pissed off with you. He says you're not going anywhere near another case - not even this one, until you've proved that you're clean.'

'Clean?'

'They drug-tested you, Sherlock. You lit up every single one of the urine dipstick tests like a Christmas tree. That was the six drug version. Then they tried the ten stick version, and you lit up pretty much every single one of those too. Tell me is there anything that you didn't take?'

'PCP' Sherlock said sleepily. 'Never touch the stuff.' The bed was comfortable, it had some kind of air mattress on it, which cushioned his aching body perfectly. He was withdrawing, not badly, he hadn't been on high enough doses of anything for the last few weeks for full withdrawal, but the come down from that quantity of medication could last for days and would be unpleasant enough.

If he wasn't allowed to work on a case then he might as well make the most of the opportunity to sleep. He hadn't been able to do much other than pace, smoke and contemplate his imminent demise for the last week. Confinement, as Mycroft had so accurately deduced, hadn't come easily to him. Too much time locked up with only his own thoughts for company rarely led to constructive conclusions. He closed his eyes.

'Hey! ' John said, shaking his shoulder. 'Wake up. I need to talk to you.'

Sherlock opened his eyes for long enough to glare at him. 'Later, John,' he said.

'No, now. How long has this been going on and why the hell didn't you tell me?'

'Tell you what?'

'Oh, I don't know - that you had a serious drug habit? That you were shooting up every time my back was turned?'

'That's what bothers you most isn't it? That I somehow deceived you.'

'Don't change the subject.'

'What would you have had me say?'

'Oh I don't know - how about, 'John, I'm using drugs and I need help to stop?'

'I don't need help.'

'Because you think that you can just stop?'

'No, because I have no intention of stopping.'

Sherlock yawned and closed his eyes. John, meanwhile, was resisting the urge to either shake or punch Sherlock for discussing his drug habit as nonchalantly as if he was discussing his refusal to stop smoking twenty Marlboro Red a day. In Sherlock's current state, however, neither was advisable.

'They think you were trying to kill yourself, you know that?' John said once he was calm enough to trust himself to speak. 'Even Mycroft isn't convinced that wasn't what you were trying to do.'

'It was a one-way mission, John,' Sherlock said drowsily. 'I didn't have to kill myself. Other people would have taken great pleasure in doing that for me.'

...

When he woke again, he was back in 221b Baker Street, but the Victorian version it. He was sitting in his chair, dozing in front of the fire and John was sitting opposite him. The modern John, not the Victorian one. And when he looked down, Sherlock found that he was wearing his normal twenty-first century clothes too - his suit, dressed for work. Dreaming or in his Mind Palace? He couldn't tell.

'Where are we?' John asked.

'Baker Street, as it was in Victorian times.'

'And why are we here?'

'I don't know. Maybe I need to work something out.'

'Any idea what?'

'None whatsoever.'

'You're going to have to tell me at some point, you know,' John said conversationally.

'Tell you what?'

John chuckled, stood up, walked over to Sherlock, and leaning over the arm of the chair, kissed him, without drama and without pre-amble.

With a start, Sherlock woke up.

It was almost dark in the hospital now, the room lit only by a single light on the corner and he was in a different room, a private room, the monitors and buzz of the intensive care unit replaced by white walls and a flat-screen television.

A figure was sitting beside his bed, and without even turning his head he knew that it was not John, but Mycroft.

'You're going to have to tell him, you know,' he said as Sherlock turned to look at him.

'Tell him what?'

'You know precisely what.'

'What happened to love being an emotion found on the losing side?'

'Without John Watson, you would have been dead years ago. We both know that. Don't throw that away.'

'I'm not throwing anything away.'

'Aren't you? Don't try to be a martyr, Sherlock. It doesn't suit you.'

'You're being ridiculous.'

'We both know that I'm not, though, don't we? You threw yourself off a roof to protect John Watson; you spent two years chasing round the world pretending to be James Bond, destroying Moriarty's network for him. And then, when you return and find that he has replaced you, you throw yourself into preserving his new relationship above all else. You make a public vow to do so, in fact. And in the name of that vow, you fail to unveil Mary Watson as the killer that she is, you protect her identity, you risk your life to ensure that John discovers the truth in a way that has the greatest chance of preserving their relationship. And then you shoot Magnussen because he humiliates John.'

'I shot Magnussen because he needed to die.'

'You shot Magnussen because you see yourself as a dragon slayer and John Watson as your damsel in distress.'

'Is that what you really think?'

'Perhaps it's time that you started being honest with yourself, Sherlock.'

'Go away, Mycroft.'

'Why? Because I'm getting too close to home?'

Mycroft leant forwards. 'Sherlock, you're into this deep - you and I both know it, and we know where it led before. You need a reason to stop using and the single reason that could possibly be powerful enough to make you do that is John Watson.'

'What makes you think that I want to stop using?'

'What makes you think that I'm going to give you a choice?'

Sherlock glared at Mycroft.

'Don't be an idiot, Sherlock. You know that I always win.'

'Go away, Mycroft,' Sherlock repeated.

'You could just tell him, you know.'

Sherlock let out a sarcastic snort. 'What - declare my undying love for him? '

'If you feel so inclined, but that's not what I'm talking about, as you are well aware.'

'Leave it, Mycroft.''

'Just tell him, Sherlock. If you don't, then I will.'

...

When he opened his eyes again, he was back in the squat. Lying on the mattress in the corner of the room, staring at the sheet that hung over the doorway in place of a door. He wasn't alone. He could hear soft breathing beside him and rolled over to look into eyes even bluer than his. Christoph's pupils were still tiny from last night's hit, making his eyes even more startling than normal.

'You need to tell him, you know.' he said.

Sherlock sighed and sat up, wrapping his arms round his skinny jeans-clad legs in an almost forgotten gesture. Sixteen years old, and already on the scrap heap. A teenage junkie, living rough, doing whatever he had to in order to pay for his habit. It was only transport after all.

'Don't you start,' he told him. He hasn't dreamt of Christoph for years, not since his last stint in rehab. It was as if moving into 221b with John had banished Christoph from his mind entirely. But part of him had returned to Sherlock's subconscious in Serbia when he was being tortured. The voice that he had heard in his head then, telling him to hold on, had always been Christoph's, never John's.

'You need to let me go, Sherlock.'

'I have.'

Christoph chuckled, a forgotten sound that still made Sherlock's heart skip uncomfortably.

'Is that what you think? I was your first proper case with the police with the police, wasn't I? You blamed yourself for my death and you set out to avenge it. If it hadn't been for Greg Lestrade, you would have ended up dead, too.'

'I should never have let you go with that punter. Not on your own. I knew he was dangerous.'

'We needed the money. You couldn't have known what he would take me into.'

'I should have realised. I should have worked it out. I should have been able to save you.'

'Sherlock, we were high as kites most of the time. We put ourselves in danger every day. You couldn't have known.'

'I should have known,' Sherlock protested stubbornly,

Christoph sighed and reached out a hand to push a curl away from Sherlock's eyes. 'I never meant for you to shut yourself off like this, you know,' he said. 'This wasn't what I wanted for you.'

Sherlock closed his eyes and reached out for Christoph's hand, but as always happened in his dreams, his hand slid straight through him, like the ghost that he was.

'Stop sacrificing yourself for those you love, Sherlock. They deserve better than that.'

'Better than being protected?'

Christoph shook his head, 'It's not just about protecting them though is it? If you love him, then you have to trust him with your past. All of your past. I wouldn't have died if it hadn't been for the drugs. You have to stop running away.'

'But he has Mary now. He has the child.'

'Does he, though?'' Christoph's reply faded, as he slowly disappeared into mist.

...

'You were talking in your sleep,' John said as Sherlock opened his eyes.

'Was I? What was I saying?'

John shook his head. 'A lot of rubbish mainly,' he said and Sherlock didn't know whether to feel relieved or disappointed.

Then John asked curiously, 'Who's Christoph?'

And Sherlock just stared at him for a long moment.

'No really, who is Christoph? You kept shouting his name and you sounded upset.'

'Tell him,' echoed Mycroft's voice in his head.

'Tell him,' whispered Christoph's voice, and it was gentle and loving in a way that it had rarely been in life.

'Tell me who he was, Sherlock,' John said. 'You were almost screaming.'

And Sherlock looked at John, hazel eyes instead of blue, but in them was the same care that had been in Christoph's. And more - in his eyes Sherlock saw compassion and understanding, and maybe, just possibly, something even deeper than that.

His closed his eyes against their power, and shook his head slightly, trying to resist the temptation to let his guard down, to just let it all out. It would be a relief, wouldn't it? To finally tell someone after all these years?

There was a hand on his arm - warm and reassuring. 'You can trust me, you know,' John said. 'Whatever it is, whatever happened, I'm still here for you.'

Sherlock swallowed hard, 'Christoph was my first case with Lestrade,' he began, but his voice cracked mid-sentence and he found himself unable to continue.

'Ask him, John,' he said, finally, when he had regained control sufficiently to trust himself to speak. 'Ask Lestrade to tell you about it. Tell him that he needs to tell you everything.'