Four hours later, Sherlock found himself sitting at one of the trestle tables at the shelter, shovelling hot food into his mouth as if he was starving. Which, now he thought about it, he probably was.

Facts were flooding back to him now that he was slowly defrosting - arctic explorers needed eight thousand calories a day to maintain their weight. Staying warm took metabolic reserve that he had never had. A quick glance in the fogged-up mirror in the men's wash room after his shower had revealed every one of his ribs. He hadn't been exactly well covered before, but now he looked positively scrawny.

Tom had been as good as his word: he had found Sherlock in the cafe, huddled next to the radiator in a warm corner, cradling a cup of tea, and had walked with him to the shelter a few streets away, chatting cheerfully all the way. Sherlock had been glad for the constant stream of conversation. He was so tired that even the short distance proved a struggle, each step punctuated by spasms of coughing that he tried to hide in his scarf. Tom had the courtesy to pretend not to notice.

The shelter itself was little more than a glorified church hall, tucked round the back of a graveyard - appropriate, Sherlock thought, to put those that society treated as invisible next to those already dead. Sherlock had almost balked when he realised it was a Salvation Army building, but Tom had calmed him with a wry grin. 'Don't worry, there isn't any obligatory bible study or anything. In fact there's no religion at all if you want to avoid it. There are a few churchy types floating around, but they're easy to avoid. I'm an atheist myself, but shhh, don't tell anybody or they might boot me out.'

Sherlock glanced at him, aware of what Tom was doing - making him a co-conspirator, turning it into them against us. It was an old psychologists trick that Sherlock was well aware of, and Tom slipped into it as easily as if he'd been trained to do so. Sherlock tried to muster up the energy to be suspicious but found himself failing. If he hadn't managed to score some diazepam, the muttering voices in his head might have added to his paranoia, but with the drugs numbing his system, he found that he just didn't care. Just for once, he was going to assume that this was exactly what it appeared to be - one well-meaning individual who wanted to expunge the guilt for some past transgression by doing a good deed. He didn't believe for a moment that Tom was just a run of the mill do-gooder; there was a sharper edge to him, one that Sherlock would have felt the itch to unravel if he hadn't been so damned tired.

It was cold now that the sun had gone down. Sherlock could see his breath in front of his face where it leached out above his scarf, coming out in staccato mists with each storm of coughing. When Tom reached out to open the door, they were hit by a blast of warm air and light, and the unmistakable sound of piped Christmas carols.

'Ah yes, I should have warned you about that,' Tom said with a grin. 'They do like a bit of festive spirit.'

Sherlock realised with a jolt that he had no idea what the date was - it seemed to have been nearly Christmas for months, the shops full of twinkling white lights, Christmas decorations, and fairytale-like scenes of happy children wrapped in hats and impractical wooly mittens at inflated prices, having snowball fights or building snowmen. But the fact that the run up to Christmas would, eventually, lead to Christmas itself had nearly escaped him.

At Christmas everything would be shut - the library, the museums, the cafes. All of the places that he went to for a few hours of warmth and the illusion of being a functioning member of a civilised society. At Christmas the world would come to a halt, as people spent time with their families and friends and convinced themselves that this strange mid-winter bubble of happiness and good will to all men was real. At Christmas, Sherlock would be cold and alone, and stuck in his sleeping bag on his cardboard box, with the hard lump of his rucksack at his feet, and there would be no distraction from the incessant thoughts causing a virtual neural snowstorm inside his head.

'What's the date?' he blurted out, breaking his own rule of minimal spontaneous speech, and realising as he did so that his accent had slipped back to his usual cut glass tone. Tom, fortunately, didn't seem to have noticed.

'December 22nd,' he replied. 'Christmas in three days.'

Christmas had never Sherlock's favourite time on year. All of that enforced socialising, all of those parties with elderly relatives and associates of his parents trying to engage him in polite conversation while he was dressed up in a suit with a tie that felt as if it was going to strangle him. He had decided from an early age that once he was an adult he was never going to wear a tie again. That had been one of the many bonuses of dropping out of school and being home tutored after Elmhurst. No tie, no uniform, no need to conform to social niceties.

'You could come here you know - for Christmas. We throw quite a party,' Tom said, not realising that he was only escalating Sherlock's anxiety levels.

Sherlock simply shrugged, pushing down the rising panic at the thought of all of that enforced socialising as he walked into the hall.

Christmas music aside it was quieter than he had imagined. There were a few volunteers chatting at the far end of the hall as they folded blankets into neat piles. More were visible through the service hatch that led to the small kitchen.

'We're not officially open yet,' Tom told him, 'I thought you might like a chance to clean up in private, before the others arrive and start banging on the door to the bathroom. Come on - this way.'

The washing facilities were basic, but clean. A row of urinals against the far wall, a couple of stalls, and two showers, side by side. The showers had doors on them that could be locked, and that was a lot more than could be said for the wash basin in the public toilets by the fruit market that Sherlock had been using to wash in for the last week or so. He had learnt to pick his times - early in the morning, when the first traders were just starting to set up, or later in the evening, when the traders had gone home. There was a brief window between the market traders leaving and the first of the local stockbrokers nipping in for a desperation piss on the way back to the tube station after one pint. The city types were the worst - the market traders tolerated Sherlock, ignoring him as he scuttled into a stall mid-wash, clutching his clothes, not wanting to be seen semi-naked. The allegedly more civilised members of society with their smart suits and overly shined shoes were often more - interactive: swearing at Sherlock, occasionally kicking out at him if he didn't get out of their vicinity quickly enough. They made him feel as if he was the scum of the earth- an irritatant, like dog shit on the bottom of their shoes, or a coffee stain on their perfectly ironed, perfectly tailored white shirts. He hated them with a passion that he was surprised to discover that he still had the energy to muster.

Inside the shower cubicle, Sherlock had stripped slowly, throwing his dirty clothes over the top of his door, not caring if they got wet. Tom had promised him the use of a washing machine later, and had already taken his spare set of clothes and his sleeping bag to wash while he showered. Sherlock had felt a twinge of panic as he handed the bag - without it he was committing himself to staying here. If he left, he would freeze outside tonight without its insulating warmth.

'Hey, relax,' Tom had told him. 'I'll get it back to you in a couple of hours.'

And there it was again - the calm manner, the anticipation of his thoughts. It reminded him of something from his past, and yet he couldn't quite work out what.

The shower was blessedly warm and Sherlock fought the effort to groan in appreciation. He had always enjoyed being clean, the feeling of fresh clothes against his skin, and the inability to wash properly had been one of the things he had found hardest since he had allowed himself to fall through the cracks. He had dared the showers at Waterloo station once, just once, picking a busy time, keeping his hood up, trusting that he wouldn't be picked up by the CCTV camera, but the bathroom attendant had unnerved him, watching him a little too closely, looking a little too much like a security man for his liking, the radio on his belt standing out like a beacon, and Sherlock had found himself walking away unwashed.

Looking down at the puddle of water accumulating by his feet, he realised that the dirt in it was all his. The realisation made him shudder. He had to find a place to wash himself and his clothes more regularly or he was never going to get through the next few weeks.

He reached out for the small container of shower gel that Tom had provided him with and soaped himself thoroughly, then repeated the process until the water ran clear before attacking his hair. Hair that hadn't been washed for several weeks proved to be surprisingly hard to get clean. It took three attempts before Sherlock could run his hands through it without grimacing. At least it was short at the moment, freshly cut for his interviews, unlike the unruly mop of curls that he usually favoured, much to Mycroft's disapproval. The haircut had been his brother's idea, as had been the tailored suit which he had protested so hard against.

'It's an interview for a place at Cambridge, Sherlock,' Mycroft has said, in a tone that Sherlock knew was his attempt at being patient, but instead came out as a mixture between disapproval and exasperation. 'You can't exactly go along in jeans and a t-shirt.'

'Why not? I thought they wanted me for my mind, not for my dress sense.'

'Because it's expected. You need to make a good impression.'

'Why do you care anyway?'

And that had been the trigger of a big argument. Yet another one in a long sequence of them. As usual it began with Sherlocks accusing Mycroft of trying to control his life, of trying to project his own ambitions onto Sherlock, and escalated into a not so polite request that Mycroft should just piss off and leave him alone. The altercation ended as it always did with the silence that Mycroft did so well; the quiet staring; the waiting, and then the habitual, crushing one-liner. Sherlock could have written the script.

'Forgive me, but I thought that you wanted to go to Cambridge. Unless you would prefer to stay here and fester for the next few years. If that is the case, then I won't stop you.'

Lacking a suitably cutting reply, Sherlock had walked out of the room, slamming the door behind him, and shut himself in his room where he turned Brahms violin concerto up to full volume and used his anger to give him the impetus to crack a tricky mathematical equation that he had been struggling with for weeks.

The next day he had got up early, showered, and then headed into the nearest town for a haircut. Feeling empowered, he had then caught the tube into London where he had taken great delight in buying the most expensive dark blue suit he could find at Mycroft's tailors on Savile Row, charging it to his brother's account.

The suit, it had turned out, had been absolutely hopeless for keeping him warm on the streets. He had quickly replaced it for jeans and a hoodie in a charity shop and dumped the suit in an industrial skip as far away from the place he was staying as he could manage. The suit would be recognisable, and he didn't want to leave Mycroft any clues.

Still, Sherlock felt a twinge of guilt when he thought about his brother, alone in their big house, walking past the big Christmas tree that they always had in the hall. Since their mother's death it had appeared almost miraculosuly overnight - put up and decorated by the house staff, like some benevolent elves. Would there be presents for him under it this year, even though Mycroft knew that he was unlikely to be there to open them? Without Sherlock there, who would leave presents for Mycroft other than those minions at work trying to curry favor, or those shady members of government for whom he had done favors over the year? Not that Sherlock's presents had ever been anything other than formulaic - a pair of cuff links, a bottle of whisky, a paperback picked from the best seller list, but they had been presents handpicked by him all the same.

Sherlock closed his eyes tightly, knowing that it was against something far darker than the shampoo stinging in his eyes. The waves of misery threatened to overwhelm him, and he quickly soaped himself a final time before stepping out into the anteroom in front of the shower to towel himself dry.

'I've got some clean clothes for you here,' came Tom's voice from just outside. 'I'll hand them over the top.'

How long had he be standing there, waiting for the noise of the shower to stop, Sherlock wondered? The thought made him feel more uncomfortable and exposed than ever. But here he was - naked, dripping, and with no clothes other than a thread-bare towel. He wasn't exactly in a position to protest - or to refuse the offer of clothes.

He reached his hand over the top of the cubicle and Tom passed him the garments one at a time - a plain t-shirt of the kind they paid kids in the third world ten pence an hour to make; a pair of light blue jeans, perfectly wearable but no longer fashionable, and a surprisingly decent plain black hoodie.

'I've got underwear for you too,' Tom said passing over a pair of new looking striped boxer shorts. 'I'll leave the socks outside with your boots, otherwise they'll get soaked on this floor.

Sherlock mumbled his thanks, and waited until he heard the door to the bathroom close before venturing out. The t-shirt and hoodie fit him well, but the jeans were far too big for him. He'd have to find a belt for them. Still, the clothes were clean, and dry, and smelt of washing powder and not of his own sweat and the grime accumulated through weeks on the street. It felt good to be clean.

He looked at himself in the mirror, wiping it with a sleeve to clear it of steam. He looked tired, dark shadow-ike bruises under his eyes. His hair was a tangled mess, and so he dug through the wash pack that Tom had provided him until he found a comb. It took him a good five minutes to wrestle out the knots, leaving his hair looking impossibly fluffy. He smoothed it into some semblance of order with water from the tap, wondering why he even cared. Maintaining his hair style hadn't exactly been at the top of his list of priorities for the last few weeks. He felt oddly exposed without the beanie hat that had been his constant headgear for the last few weeks, but was now in the washing machine with the rest of his clothing.

He cleaned his teeth quickly,realising that the noise level had started to rise outside, indicating that other rough sleepers were arriving. Sherlock wondered how quickly his sleeping bag would be dry, in case he needed to make a break for it. He stuffed the shaving kit back into his rucksack unused - he was keeping the stubble in the hope that it would make him less recognisable from the picture that Mycroft was no doubt still having circulated of him.

Finally, he dug into the bottom of his rucksack for the watch that he had inherited from his grandfather. He hadn't been able to bring himself to sell it, no matter how short of cash he had been, prefering to pick pockets for cash instead. He told himself that it was too easily identifiable to sell - a sure way to direct Mycroft's attention to his location. As if sentiment and keeping one piece of home with him had nothing to do with it.

Then shoving his feet back into his boots, Sherlock took a deep breath and walked out of the bathroom to face the noise and people outside.