"Right, that's me knocking it on the head for Christmas," Lestrade announced, clapping his hands together, and rubbing them a little in the cold. "Pleasure as always, boys."

Sherlock looked up from his phone.

"You're finishing for the day?" he demanded, brow furrowed in confusion. "It's four o'clock."

"Yeah," Lestrade smiled. "A key piece of evidence secured, a couple of big arrests and some extradition warrants issued – pretty satisfying day's work. Credit where credit's due, Sherlock – it's mostly down to you that I'm getting my Christmas Eve early finish."

Sherlock glanced across to John, who apparently didn't share his confusion and seemed to be surveying the scene with some amusement.

"Do you mean to tell me that the criminal classes honour the feast days of the Gregorian calendar and break for Christmas?"

"Aahh, nope," Greg replied. "But even if they don't want a holiday, I do. Besides, I'm back on shift again at eight am Boxing Day, so I'm taking every extra hour I can get."

Sherlock sighed, pocketing his phone.

"Well, what about that double murder over in Harpenden? You said you wanted our help with it."

"The cold case?" Lestrade replied. "It's a cold case, mate. It's not going to get any colder over the next two days."

Sherlock frowned, shifting uncomfortably from one foot to the other. This day was not concluding as he expected it to, and the spectre of aimless hours now loomed ahead.

"So what are you doing, then?" he queried. As if I don't know the answer.

"Pub," Lestrade replied. "We're all decamping to The Red Lion to make merry with some quality ales and erudite conversation."

Sherlock snorted. He would be pissed and talking absolute drivel by five-thirty.

"You can join us if you like" the detective offered. "Both of you. I'll even get the first round in."

"Thanks for the offer, Greg," John said, before Sherlock could reply. "But if I leave now, I can get Rosie from the childminder a bit early and have a few hours with her. Feels as though I haven't seen her properly for ages."

That was fair enough. Sherlock had been feeling slightly guilty about the volume of cases he'd taken on in the past few weeks, knowing it was keeping John from his daughter, just to fulfil his own recent compulsion to keep busy. He didn't like to think too closely what was behind that compulsion.

Lestrade treated them both to one of his customary bear-hugs, and drew this coat collar around his neck.

"Have a good one," he told them. "What time should I be there tomorrow?"

"Mrs Hudson wants us all around the table at one, but come over earlier if you like," John replied. "Sherlock can treat us to some Christmas tunes."

Sherlock rolled his eyes.

"If you change your mind, Sherlock, you know where we are," Lestrade said, as he backed away with a wave.

"Indeed," Sherlock replied. "And you should probably know that the redhead from the forensics unit - for whom you're wearing the cashmere scarf and Tom Ford cologne - is actually seeing someone."

"Merry Christmas, you grumpy bastard!" Lestrade called, apparently undeterred.

Sherlock and John started to walk towards the main road together, Sherlock retrieving his phone from his pocket again. No emails, no blog activity…one new text. Molly's name flashed up on the screen; swallowing, Sherlock restored the phone – message unread – to his pocket. Eight years ago, he had hastily jabbed the name 'Pathologist – Bart's' into his address book; there had been a need to exchange mobile numbers, so she could text him some lab results. A couple of weeks later, he had amended that to 'Molly Hooper – Bart's'; a few months on and he'd shorted it to just 'Molly Hooper', and that was the way it had stayed until earlier this year. But a few months ago, he had found himself changing her contact details in his phone again – and now she was simply 'Molly'. Anything else seemed superfluous.

"Do you want to come and have an early dinner with me and Rosie?" John asked. "Just leftovers, but I know she'd loved to see you."

Sherlock smiled, glancing across at John.

"She'll see me tomorrow," he replied. "She needs to be with her father tonight."

"Okay, so what about you?" John asked, stuffing his hands into his pockets. "What are you going to do with the rest of your Christmas Eve?"

"I suppose I'll go home."

The corners of John's mouth turned down as he gave it some thought.

"What about your brother?" he said eventually. "You could go and have a drink with him. He's probably at his club, isn't he?"

Sherlock snorted. Yes, Mycroft would almost certainly be ensconced in the oak-panelled sanctuary of the Diogenes Club, nursing the four-hundred-pound whiskey that he gifted to himself every Christmas and very definitely not wanting to be interrupted by his twitchy, preoccupied little brother. Worse still, Mycroft would probably successfully deduce why he was feeling this way, and Sherlock wasn't ready to have that conversation.

"It will be an opportunity for me to catch up with one or two of the projects I've been neglecting of late," Sherlock said briskly. "That monograph I've been writing about pollen types, for example. I'm also halfway through a series of experiments examining the use of seemingly innocuous cleaning in apparent incidents of poisoning."

John raised his eyebrows and puffed out his cheeks.

"Wow. That does sound like Christmas treat," he replied. There was a short pause as they walked, which ended when John looked as though he'd been struck by a lightning rod of genius. "Hey, why don't you ask Molly to come over? I think she was going to some drinks thing straight after work, but it's not a late one. If you're insisting on doing experiments on Christmas Eve, she'd probably be happy to keep you company."

Keep me company. Is this what things had come to?

"Thank you, John, but I am not doing to die of loneliness in the course of one evening," Sherlock replied curtly. "Besides, I'm sure Molly will have something better to do – something nauseatingly festive, no doubt. You're forgetting, John – Molly likes Christmas."

John rolled his eyes.

"Yeah, yeah, and you think it's an international capitalist scam designed to keep us all in thrall to tradition and enslaved to material spending, and based on a nonsensical concoction of Pagan, Judeo-Christian and Victorian customs," he said. "Did I miss anything?"

Sherlock made a hmph noise.

"Sounds about right," he replied. "Although you forgot the bit about being forced to pretend that there's merit in spending time with one's blood relatives."

He paused to re-tie his scarf.

"Look, Molly does enjoy Christmas, yes," John pushed. "But you know Molly – friends come first with her."

He really wished John would let this one drop, but if he wasn't going to rouse any suspicion with his friend, it would be best to keep things cordial.

"I'll be absolutely fine," Sherlock replied. "I may even take some time to reorganise my Mind Palace."

By this time, John had managed to flag down a cab and, having greeted the driver, turned back to Sherlock before getting in.

"Yeah, well, as long as you don't spend all night trawling the web for signs of criminal activity, or arguing with nut-jobs on conspiracy theory sites," he grinned.

"Give my love to Rosamund," Sherlock replied, ignoring the dig.

As the black cab pulled out into the waiting line of traffic, Sherlock turned to head in the opposite direction. He only lasted a few seconds before he took out his phone and swiped to the unread text message.

Home about 8. I have mince pies, cheese footballs, gingernuts and Bailey's. Be better if I didn't finish them myself – MH

She had included a smiley face emoji, which Sherlock should have found hateful. But, for a while now, he hadn't. Well, she was the exception to this rule – as with so many other of the rules he had set for himself over the years, and more and more as this year had gone on.

The truth was, Molly had invited him over to hers several days ago. He hadn't promised he would go, but he hadn't exactly said he wouldn't either; he should probably have been more emphatic about that – although to do that, he would first have needed to make a decision.

The invitation was friendly, casual – but it absolutely terrified him. It was exactly what he didn't need, exactly what he had been trying to avoid, because the fact was that he no longer trusted himself. He couldn't afford to put himself in a position where there was even a chance he could do something stupid, something that would invariably hurt Molly again.

He had managed to navigate his way through the last few months with more luck than judgement. In the immediate aftermath of Sherrinford, he had assumed that he probably destroyed the last vestiges of friendship that existed between himself and Molly; that he had obliterated her trust and lost every ounce of he regard. Although he was not to blame for the circumstances, Sherlock knew he could have behaved better during that phone call – when he could bear to reflect on it, he could hear his flippancy, his arrogance, his belittling of something that he now realised was incredibly precious, and of which he was completely undeserving.

The lead-up to that first conversation after Sherrinford had been agonising, and when he was finally face to face with Molly, all articulacy deserted him. He'd fumbled some sort of apology, and said something about what he'd said on the phone being "not entirely untrue". Molly had replied that she knew he his intentions had been good in wanting to save her, that she understood there were different permutations of love, and that they should probably draw a line underneath the whole episode.

In short, she'd made it easy for him – easier than he deserved. Perhaps it was because he had left it too long, given Molly time to find that pragmatism that he so admired in her, given himself time to try to rationalise everything. Perhaps if the raw hurt had still been there, it would have been a different conversation – possibly with a different outcome. It was only after that conversation, when he was alone again, that he realied that perhaps 'drawing a line' wasn't what he wanted; it felt too final, like a door was being closed,

Sherlock picked up his own cab a couple of streets on, arriving back at Baker Street just in time to find Mrs Hudson leaving her flat, struggling to lock the door while balancing giftbags. He took them from her arms, earning a surprised look in response.

"Oh, thank you, dear," she said, returning her keys to her handbag. "What's got into you this evening?"

"Nothing!" Sherlock replied, immediately realising how defensive it sounded. He quickly recovered himself. "Next time I'm happy to let you continue in your struggle."

"I'm just off to a little get-together with my Zumba ladies," his landlady told him. "What time are you going out?"

Sherlock inwardly rolled his eyes (but at least it was inwardly this time).

"I'm not."

Mrs Hudson looked at him as though he was being a particularly trying toddler.

"Oh, Sherlock, you can't just stay in by yourself on Christmas Eve!" she cried.

For a moment, he was worried that he was about to be invited to spend Christmas Eve with a dozen elderly ladies tanked up on G&Ts.

"Why not? I've coped with it every year up to this point," he protested. "And on the occasions when I haven't been free to do so, believe me Mrs Hudson, staying in by myself is exactly what I craved."

Mrs Hudson tutted at him, shaking her head.

"Go on, get yourself out!" she insisted. "Do something with your evening!"

"I intend to," Sherlock replied. "It's currently sitting in a half-finished state on the kitchen table."

"I know what you should do!" she said, as she tucked her hair into her woollen hat. "Why don't you go over to Molly's? I know she'd like to see you. Take her some Christmas cake if you like, dear; it's in a tin on top of my fridge."

"I know," he told her with a small smile. "It's very good."

Mrs Hudson gave him a long-suffering look, but Sherlock could tell that he had time on his side here; Hudders was in a hurry, so she'd have to give up the argument sooner or later.

"You should really think about it, Sherlock," she told him, smiling at him with the kind of earnestness that he found it very difficult to be glib with. "It's the time of year for it, isn't it?"

He didn't dare to ask what it was that she thought it was the time of year for; he probably wouldn't like the answer.

A few minutes later, he was safely installed in the kitchen of 221B, fire ablaze in the sitting room hearth (he'd have to thank Hudders for that in the morning), goggles and gloves on, and Bunsen burner ready. Sherlock scrolled back through his notes on his laptop, reminding himself of his earlier results and the remaining tests he wished to run.

His phone buzzed on the kitchen counter, and his heart leapt to an embarrassing degree. He flipped up his goggles and waved one glove off his hand to pick up the phone and open the text.

You have unused data on your plan this month. This will roll over into next month's usage. Why not call us about switching to a plan that works for you? To stop receiving these messages, reply with STOP.

Sherlock let out a low grunt before returning to his experiment. It had been bad enough before, but now all he could think about was Molly's text. Maybe he should have replied. He could have said that a case had come up - but it was a lie that would inevitably be exposed the next day around the dinner table, and that would be more than a Bit Not Good. And lies were no longer an option, anyway; although he hadn't said it out loud to Molly, Sherlock had vowed to himself that after Sherrinford, he would be nothing but honest with her.

How's that working out? he heard Mind Palace John asked.

He had assumed that after That Phone Call, Molly would want to put some distance between them, but the reality was exactly the opposite. She made no effort to avoid him, and always seemed pleased to see him. And once he understood that he wasn't completely persona non grata, Sherlock found himself looking for opportunities for them to be in the same place at the same time. He hadn't liked to admit that was what he was doing, but he knew full well what it would look like to even an objective observer. Extra hours in the lab of Bart's, doing work that they both knew he could be doing at home; coming by when Molly was babysitting Rosie; turning up with take-away food just after she got in from work.

He knew what was happening to him – no, what had happened to him - and that's why he'd needed to put an end to it.

It wasn't difficult to increase his workload; there was never a lack of cases jostling for his attention – he just had to lower his standards. Significantly lower his standards. Some of the crimes were so mind-numbingly boring that Sherlock had wanted to repeatedly bang his head against the nearest doorframe - and even John started to query why he kept taking such pedestrian cases.

But it kept him busy, meant that should Molly ask, he could tell her that he was working and it wouldn't be a lie. And he started doing more lab work at home, hence the half-arsed piece of work in front of him.

With a sigh, Sherlock poured a measure of sodium hypochlorite into a beaker, setting it down on the bench beside him. The kitchen table was an unruly mess, nothing like the nice, clean, ordered lab at Bart's. Years ago, Molly used to clean up after him after he left, but these days she would smile and throw cleaning cloths at him, reminding him that he needed to return equipment to the cupboard. And more often than not, they would leave together, after which he would walk Molly to the Tube, or they would go for food – or he would get an invitation to come back to hers.

The sample needed to be diluted as per the previous experiment, and Sherlock reached for the beaker of tap water he'd poured earlier.

Back to hers. Sherlock thought about Molly's original invitation to come over tonight, and the recent text; he imagined a tree adorned with a variety of mismatched and probably slightly odd decorations, terrible Christmas music coming from her laptop, and Molly in the reindeer pyjamas he knew that she owned (bolthole days all those years ago were dull, and the contents of no drawer remained a mystery).

It would be so easy to stop what he was doing right now and hail a cab. But then where the hell would he be? Two months of careful distancing completely undone because he…he missed her.

Bloody Christmas.

Sherlock added the 250ml of water to the sodium hypochlorite and-

"Ohh…shit!"

Apparently, that wasn't water.

Almost right away he started to feel dizzy, disoriented. Sherlock coughed, spat, rubbed his eyes and tried to reach for the actual beaker of tap water, but already his limbs seemed to be unwilling to cooperate with his thoughts. He tried to make it to his phone, but all he managed to do was clumsily swipe it onto the floor.

His eyes rolled back in his head, his legs went completely from under him and everything went black.