The story so far:

This story was written post s2 and pre s3, so the BBC canon is accurate up to that point.

Sherlock is ill with psychotic depression. John and his girlfriend Kate (see the Girl in the Scarf for the background have been looking after him with the help of the psychiatrist, Ed Harris. He has told them that he had a similar episode as a teenager and spent several months in a psychiatric hospital before Mycroft signed him out and brought him home.

All has been going well and he has slowly been getting better. But as we all know, with Sherlock, things are rarely as they seem...

She should have known, should have remembered that the danger time is not when people are at their lowest. It comes when they start to come back up towards the surface, and then feel themselves sinking once more. When they remember how it felt to be drowning, and know with certainty that it could all happen again.

Everything had seemed calm, so calm. Sherlock had been quiet, but then he was often quiet these days. John was still spending the days with Sherlock, while Kate was back at work. They were both wary of leaving him alone, despite his protestations. 'Baby-sitting,' he called it, but Kate knew that in reality he feared the silence of being left alone. He was frustrated at not being able to work, but a possible date for a return to cold cases was already being discussed with Ed Harris. There were still issues that he wouldn't or couldn't discuss, and his days were still split between therapy sessions and sleep. Seeing him immobile for long periods of the day seemed odd to Kate, but Ed reassured her that it was Sherlock's ways of managing his symptoms and the side-effects of the medication. 'It will improve with time,' he told her. 'It's just his way of coping. Best not to interfere with that for now.'

She couldn't say what had woken her. The old fashioned alarm clock on the bedside table read ten past three. The bed beside her was cold and empty. She checked the bathroom and the kitchen. Both empty. His coat was gone, his phone when she rang it went unanswered. Fighting down the rising panic, she phoned John.

'John, he's gone. He must have found my keys.' She had taken to hiding her keys at night, just in case, but in retrospect the back of the cutlery drawer probably wasn't such an intelligent hiding place when you were dealing with a consulting detective.

'I'll be right up.'

She tried to track his phone on-line, but his account was of course, impossible to hack into. His phone was still ringing out. She sent him a string of text messages, with no reply.

'Where would he have gone?' she asked John. The look on his face said it all, neither of them knew where, but they both knew why.

'Mycroft,' Kate said suddenly, pulling out her phone. 'He'll be able to find him, won't he?'

Mycroft, unsurprisingly was up and working. He listened to Kate's hurried explanations in silence, then said only, 'Of course, I'll get my people onto it immediately.'

Kate barely had time to get dressed before Mycroft rang her back. 'He's at Barts, or at least his phone is. I'm on my way.'

'Christ, the roof,' said John

'Why not the lab,' said Kate, but even as the words came out of her mouth, she knew that he was right. By some miracle they managed to find a cab as they were running down Baker Street, and were at a Barts less than ten minutes later.

'You try the lab, I'll go to the roof,' Kate said to John, as they ran into the building.

She found him huddled up in a corner, his dark coat blending into the shadows, having a furious conversation with himself. Safe, then, for now.

'Sherlock,' she said warily, suddenly wondering if he was sleepwalking again. She had found him wandering the flat with nightmares several times in the past few weeks.

His face, when he finally raised it off his knees to look at her told her everything. He shook his head slowly, as if speaking was too much effort. 'I can't Kate, I'm sorry,' was all that he would say.

She sat with him there, arms around him, trying to warm him with the heat of her body, vaguely aware of flashing blue lights below, but unwilling to leave him even to get help. At least while she was holding onto him she could keep him safe. Out of the corner of her eye, she saw John emerge from the fire door at the top of the stairs at speed, but he slowed and stopped when he saw them, not wanting to startle Sherlock. But Sherlock did not even seem to register his presence. John took his phone out of his pocket and lifted it up in question, without speaking. Kate nodded back, silently agreeing to what John was asking. 'Yes, tell Mycroft. Get some help up here. Keep him safe'.

Ten minutes later, Sherlock was being escorted off the roof, blinding stumbling down the stairs like a drunk man, supported by Kate. He hadn't spoken another word. If it hadn't been for that initial recognition, Kate could almost have believed him to be sleepwalking. Shut down, catatonic. She knew exactly what was happening to him.

Mycroft was waiting outside his car at the bottom and took a step towards them. Kate shook her head, as she and John manoeuvred Sherlock into the waiting car.

'Sherlock, stay here with John, I'll be back in a minute,' she said. He didn't respond, just sat back against the seat, eyes closed, unresponsive, trapped with his own demons.

She walked over to Mycroft. 'Thank you,' she said, quietly.

'How long, Kate?' he asked.

'Four weeks, a little more.'

'I warned you, Kate,' he said; the words spoken with sorrow, not with malice.

'I know. I told you that I would get him through it, and I am. John and I both are.'

'Is he seeing someone? A psychiatrist?'

'Of course, but I don't think that it's enough, not anymore.'

'You could have asked for help before.'

'He didn't want you to know. He didn't want anyone to know. I'm sorry, Mycroft.'

'Will he let me help now?'

'I think so. I don't think that we have a choice. Not if we want to keep him safe.'

Mycroft nodded. 'Who is his psychiatrist?' he asked.

'Ed Harris, I think that you know him.'

'Of course, he's a good man. He's looked after several of my employees in the past. I'll contact him. There is a clinic that the service uses, Ed Harris has admitting rights there. It would undoubtably be the best place for Sherlock to go.'

Kate hesitated, caught between the logic of what Mycroft was proposing and her desperate need to keep Sherlock safe with her.

'Kate, we have to keep him safe. You, I think, can no longer do that. You have asked for my help tonight. Let me provide that. Let me help him.'

Kate was surprised at this rare expression of compassion from Mycroft. She had never seen any expression of love from either brother, and this was the closest to emotion she had ever seen Mycroft convey.

'He is my brother, Kate,' he said, with feeling. 'I won't stand by and watch him destroy himself.'

Not a threat, thought Kate, but an expression of concern. How interesting.

'He refused admission before,' she said, 'Ed Harris has suggested it many times, but now...'

'Now, he does not appear to be in a condition to refuse anything,' Mycroft said quietly. 'Still if Ed Harris can persuade him, then that would be simpler than a section. Although it wouldn't be the first time that it has come to that.'

'He told me,' Kate said quickly, then, 'I want to take him home, Mycroft, back to Baker Street. We'll contact Ed Harris from there, get him to come and see Sherlock and see what he says.'

'There is only one possible option, Kate,' Mycroft said. 'Only one way to keep him safe.'

'I know,' Kate said, 'but not like this. Not in the middle of the night and without his consent. I want to get him back to a place that he knows and people that he trusts. He trusts Ed Harris, he'll take it better from him than from a stranger in an unfamiliar place.'

Mycroft looked at her with interest, as if he was processing her intent. Finally he said, 'My brother is very fortunate, Kate, to have found someone who cares for him as much as you do, but I won't have him put at risk.'

'Then put a guard outside the door, where we can call them if we need them,' Kate said, 'I'm not denying what needs to happen, Mycroft, I'm just trying to make it as gentle as possible for Sherlock.'

Mycroft nodded slightly, 'Very well,' he said, 'and I will have a car put at your disposal for tomorrow morning, to take him in the clinic. If there's anything that you need in the meantime, anything at all...'

'Then I'll call. Thank you, Mycroft,' Kate said, wondering why this display of compassion was threatening to reduce her to tears when nothing else had. She walked quickly back to the car where Sherlock and John were waiting.

...

Sherlock was silent on the way home, eyes closed, head resting against the back of the seat. John had procured a blanket from the paramedics, who Sherlock had refused to allow near him. The heating in the car was turned up full blast, but Sherlock's hand, when Kate reached for it, was still icy cold.

Arriving back at the flat, Kate tried to ignore the second car, which had followed them back and was now parked outside 221B. Mycroft's guards, of course, but for once she was grateful for them. This time she wanted Sherlock watched, wanted him kept safe.

Sherlock walked silently into the flat and threw himself down onto the sofa; half sitting, half lying, head resting against the sofa back, eyes closed.

'You should get into bed,' Kate said gently, sitting on the sofa next to him. 'Try and warm up a bit, you're still freezing,' but he just shook his head and remained immobile. He didn't protest, however, when she placed a duvet over him, just remained immobile, eyes closed.

'Do you need anything? Lorazepam?' she asked, but he just shook his head. 'Shout if you want anything,' she said finally, when he remained silent, before going to join John in the kitchen. John slid the door almost shut behind her, leaving it open just enough to enable him to watch Sherlock while they talked.

'What did Mycroft say?' he asked quietly.

'He's organising his admission to the clinic that Ed Harris talked about for this morning. I gave him Ed's name, but we ought to phone him first, I suppose.'

John nodded, watching her face. 'It's the only option, Kate, you know that. When I think about how close it came..'

'I know, I know,' Kate said, sinking down into one of the kitchen chairs. 'But it came out of nowhere, John. Did you see this coming?'

'Not remotely,' John said, seating himself so that he could still see Sherlock, who hadn't moved since they had left him. Was he asleep? Possibly, although his breathing seemed too quiet for that. 'He seemed - fine,' John continued. 'A little quiet maybe, a little withdrawn, but thats about it. I don't think that any of us could have seen this coming.'

'So what now?' Kate asked. 'I don't know how to raise the question of an admission with him.'

'And I don't think that you should. I'll phone Ed, get him to come round and see Sherlock. He needs him now more than he needs us. Look at him, Kate. Goodness only knows what's going on inside that head of his, and he's obviously not going to talk to us.'

Kate looked at her watch. 5.45am. 'Perhaps we should leave it a few hours,' she said hesitantly, but John shook his head. 'Ed needs to know now, Kate. Sherlock is his clinical responsibility after all, and if he'd carried through his plans tonight, then it would have been his head on the block in the coroner's court. Besides, better for him to hear it from us than from Mycroft.'