It had been Mary's idea to check on him. Although it was fairly unusual to hear nothing at all from Sherlock for a few days, John wasn't particularly concerned, and had resisted her 'suggestion'. The fact that Sherlock hadn't responded to texts or even to Mary's email about the wedding venue suggested disinterest - or sulking - rather than anything more insidious. Still, it had become clear that Mary wasn't going to let him rest until they had first-hand evidence of Sherlock's wellbeing - except she had a shift at the clinic that day, so it was John alone who let himself into 221 Baker Street, automatically wiping his shoes before Mrs Hudson sprang out of 221A and caught him doing otherwise.

From the bottom of the stairs, he could hear the sound of muffled music. He was used to Sherlock's long, drawn-out violin sessions - they were usually depressingly mournful or gratingly frenetic, and either invariably made John want to throw his newspaper (or laptop) at his friend. But this was recorded music, a whole orchestra. There was no response when John knocked at the door of the flat, but when he took the decision to go in, he was greeted by a sudden and fairly startling trumpet flourish.

Across the living room, Sherlock was standing by his desk, his hands clasped behind his back and his lips pursed. He acknowledged John with the merest quirk of his eyebrow.

"Appreciate the entrance music, Sherlock, thank you," John said, grinning, unable to resist. "So, what happens now? Do I get a knighthood?"

"It's better, don't you think?" Sherlock said, apparently ignoring him.

"Er, that depends," John replied, with a bemused frown. "Than thrash-metal or free-form jazz? Yep, definitely."

Sherlock gave what looked like a sigh of sufferance.

"It's 'The Prince of Denmark's March' by Jeremiah Clarke," he said. "Originally attributed to Henry Purcell, of course. Anyway, it's less obvious than the Wagner. Everyone will be expecting that."

John finally felt as though he was starting to catch up.

"You're talking about 'The Wedding March', right?" he said.

"Nooo," Sherlock said, with dwindling patience. "'The Wedding March' is Mendelssohn, the 'Bridal Chorus' is Wagner. Why does everyone always confuse the two? Both incredibly clichéd, though, which is why I think there should be something that adds just that little element of surprise."

John folded his arms, narrowing his eyes at Sherlock.

"Not sure that's why people go to weddings, Sherlock."

He saw a look of mild distaste come over Sherlock's face.

"Yes, well, that's the one thing during my research that I haven't been able to satisfactorily discover," he said.

"Your research?" John asked, carefully, almost afraid to. Although he knew what was going on, he also had no idea what was going on - which was a very familiar position to be in, when it came to Sherlock.

Sherlock gave a hum of affirmation, and gestured vaguely over his shoulder. That was when John finally took proper notice of the living room wall - and acknowledged that Sherlock maybe had a point when he accused him of seeing rather than observing.

"Dear-God-in-Heaven-what-is-going-on-here?" he blurted, still trying to absorb what was in front of him.

What John was traditionally used to seeing in this spot was a 'murder wall', plastered in news clippings, maps, photographs of victims and suspects, index cards, and hastily scrawled ideas, often messily connected up with drawing pins and red string. What he was not expecting to see was...whatever this was. He took a couple of steps closer for confirmation, taking in the cuttings from what seemed to be wedding magazines, along with numerous fabric samples, colour schemes torn out of paint catalogues, pictures of floral arrangements, and what looked very much like floor plans of both St Mary's Church in Sutton Mallet and the hotel for the reception.

It might be wedding-themed, but it was still bloody disturbing.

"Just a few...concepts," Sherlock replied, mildly, with a tilt of his head. He crossed to the table and removed his phone from the speaker-dock, abruptly silencing the trumpets, mid-flourish.

"For our wedding?" John said, slowly.

"Yours and Mary's, yes," Sherlock replied.

"Well, yeah, obviously I didn't mean our wedding," John said, gesturing between the two of them. "Although I think that off-the-shoulder dress might look pretty good on you."

He also suspected that Mrs Hudson might have the plans for that wedding covered, just on the off-chance.

Sherlock rolled his eyes, and went back to what he'd been doing when John arrived, holding blank pieces of paper up to the light one after another, before placing them in one of two piles on his desk. When John looked more closely, he realised that both the desk and the coffee table were stacked with wedding-related books, most of which had pages marked with a system of different-coloured sticky-notes. He was starting to think that Mary was right to want to check on Sherlock.

"Sherlock," John began, taking a breath. "What's going on?"

Sherlock glanced up, brow furrowed.

"What?" he queried.

In response, John challenged him with a look. Sherlock shrugged.

"I was merely concerned that we don't have long to pull this wedding together," he said. "I mean, have you even thought about a seating plan yet?"

"We haven't even thought about guests yet," John told him. "Although at least we do now have an orangery to put them in. Seriously, Sherlock, what's going on with you? A few days ago, I thought we'd have to stage a kidnapping to get you to the wedding, and now…"

At this, Sherlock actually looked slightly put-out.

"I thought you and Mary would appreciate me taking my role as Best Man seriously," he said, slightly indignantly.

"Yeah, it's great" John nodded. "But this is more like Wedding Planner than Best Man."

Sherlock shrugged, furrowing his brow again.

"Then isn't this better?"

John opened his mouth to answer, then decided against it. Clearly, Sherlock was always either going to take a case in Australia in order to avoid attending the wedding, or he was going to do something like this - some midway point was out of the question. John gestured to the pieces of paper Sherlock was still holding.

"Are they...?"

"Samples of paper for the invitations, yes," Sherlock replied. "I can't decide between the cotton fibre or the linen finish; I'm separating these into nos and maybes. You're not planning to include an owl or alternative bird of prey in the ceremony, are you? I've been watching videos on YouTube and it's apparently a thing – owls delivering the wedding rings during the ceremony – although judging by some of the videos, the margin for error is fairly substantial."

John was caught off-guard by this complete non-sequitur.

"Hang on - owls? Er, no, I don't think so - Mary is frightened of them."

Sherlock gave him a curious, dubious look.

"Mmm, no she isn't."

"Yeah," John persisted, feeling the back of his neck grow a little warmer (damnit). "She is."

Sherlock continued to stare.

"Okay, fine!" John said, throwing up his hands. "I'm frightened of them! No owls."

"No owls," Sherlock repeated, as he actually noted down this fact on his phone. "Tea?"

John accepted the offer, though he followed Sherlock into the kitchen, mindful of the last cup of tea he saw Sherlock prepare at Baker Street. The sight of Sherlock's phone had also prompted John to remember something he was supposed to do - that is, Mary had made him promise he would do. He dug his own device out of his pocket, clicking until he reached the folder of photos.

"So, ah, how did things go the other day, in the end?" John asked. "When Molly stood in for us?"

Sherlock's gaze flicked up at him from where he was examining mugs on the draining board.

"It was fine. Thank you," Sherlock replied. "The cases were disappointingly mundane, but Molly had come all that way - thanks to your fiancée - so I didn't like to just call the whole thing off."

John cleared his throat.

"Mary found this," he said. He held out his phone to show Sherlock the webpage from MailOnline that Mary had shoved in his face the previous night when he'd been attempting to sleep.

Sherlock approached the phone screen with a cautious, poker-faced expression. He scanned it for little more than a second, but before Sherlock's brow wrinkled in a display of mild disgust and exasperation, John noticed something else flash momentarily across his friend's face. John wasn't sure what he was expecting, but now he was slightly curious; it reminded him of the moment that Sherlock first clapped eyes on Molly's fiancé, one of the few times when he'd seen Sherlock Holmes genuinely speechless.

"'Hat Detective hunts down perfect love-nest with mystery brunette'," John read aloud, deciding to enjoy the moment. "Hope Tom doesn't browse the gossip sites in his lunch hour."

The accompanying photo had been a bit of a surprise, John conceded (although it still didn't warrant being prodded awake at 11.30pm). Whichever opportunist toe-rag had taken the slightly wonky shot on their phone and then blabbed to press had managed to capture Sherlock and Molly apparently looking around a swanky-looking flat together. John supposed that would have been enough on its own, but the fact that they were standing very close together - and Sherlock's hand was lingering at Molly's lower back - was a bit more incriminating. Or at least it might be more incriminating if this was anybody but Sherlock.

"That flat was a key focal point for the investigation," Sherlock replied, gruffly. He stuffed two teabags into the British Isles teapot.

"Yeah," John smiled. "But even you must see it looks a bit not good."

"I don't see anything of the sort," Sherlock said, flicking the switch on the kettle. "But then again, I'm not a crass, feeble-minded idiot. What colour is Mary thinking of for the bridesmaids? We can't have them clashing with the floral displays."

John kept his eyes on Sherlock while he pocketed his phone again; the consulting detective seemed genuinely a little rattled. A fear of Tom seemed extremely unlikely; a fear of upsetting Molly was possible, he supposed.

"Not a clue," John replied. "Look, I'm really grateful, honestly, that you're putting so much into this, but you know it's customary to let the bride and groom have a say in some of this stuff." He thought about a few of the wedding-themed conversations he'd had with Mary so far, and revised that statement. "Well, the bride, anyway."

Sherlock gave a sort of half-nod of acknowledgment, and started evaluating a series of different styles of envelope while he waited for the kettle to boil. Conversation clearly not forthcoming, John made a tentative step towards the 'wedding wall', daring himself to look more closely at Sherlock's collage masterpiece (which included photos of Mary and himself, helpfully labelled Subject A: The Bride' and 'Subject B: The Groom').

From where Sherlock was standing at his desk, he cleared his throat lightly.

"Has...has Mary chosen a chief bridesmaid yet?"

It was Sherlock's tone that made John turn around: casual in that way that is so contrived it sounds anything but casual.

"Yeah, I think so," John told him. "She's just waiting to ask her. Her name's Janine; she and Mary used to work together briefly, I think. I've only met her a couple of times, but she seems nice - you know, fun."

Sherlock nodded slowly.

"Why are you asking?" John continued.

If the tables were turned and he was the single Best Man, then yeah, he might have an interest in finding out about the chief bridesmaid; but even with his newfound interest in the trappings and traditions of weddings, it seemed unlikely that Sherlock was looking to tick that particular box.

An evasive look came over Sherlock's face, as he turned to walk back to the kitchen.

"Nothing. No reason," he replied. "Only...it had occurred that perhaps Mary might have considered Molly for the role."

John opened his mouth to respond, but Sherlock beat him to it.

"They're friends, aren't they? And Molly possesses excellent organisational and problem-solving skills. She's punctual, reliable, and calm in a crisis."

John couldn't help giving a snort of laughter.

"Yeah, well, if someone needs to fake a death during the wedding, we know Molly's got that covered."

"What's more", Sherlock continued, undeterred. "I believe that she is not averse to a social gathering based largely around alcohol consumption, and that on occasion she enjoys wearing an overpriced dress. She also likes flowers. I think that just about covers the duties of chief bridesmaid, doesn't it?"

"Well, there's the dancing, too..." John replied, raising an eyebrow.

He saw Sherlock's eyes widen momentarily, before adopting a testy frown.

"Yes, well, she probably doesn't mind that either," he said, quickly, as he poured boiling water into the waiting teapot.

John followed him back into the kitchen, pausing by the table.

"Sherlock," he began. "Molly didn't put you up to this, did she? The other day?"

At this, Sherlock's eyes shot up, and he looked positively appalled.

"Of course not!" he replied, tersely. "Molly would never...and besides, the other day was work; it was strictly professional. Believe it or not, we did not spend the entire day gossiping about the minutiae of your nuptials."

It was tempting to poke the hornet's nest a bit more for his own amusement, but John knew that Mary would want him to keep Sherlock on side - if she found out he'd trampled all over Sherlock's nascent wedding enthusiasm, it wouldn't even be the sofa he'd be sleeping on, it would be the pavement.

"Seriously, though, Mary was actually talking about Molly and the bridesmaid thing," John said, hitching himself onto one of the kitchen stools. "But she reckons they might be going through a rough patch, Molly and Tom."

"Really?" Sherlock said, looking up again. He cleared his throat quietly, straightening up. "I mean...really?"

"Mary and Molly were supposed to go and look at wedding dresses, or something, and Molly cancelled at the last minute," John said, shrugging. Personally, he wasn't sure that one cancelled dress-shopping outing equalled imminent relationship meltdown, but Mary clearly saw it differently. "Anyway, now Mary is worried about Molly having to be caught up in planning someone else's wedding, if things with Tom are...well, you know. Could be a bit awkward."

Sherlock gave a thoughtful nod.

"And Molly is great," John added. "But I'm not sure whether she's a hen-do kind of person - you know, big group of women, lots of Prosecco, L-plates, novelty things shaped like male...appendages."

At this, John saw Sherlock visibly blanch (he was clearly in for a tame stag-do, if this reaction was anything to go by).

"Anyway, I think this Janine is exactly that kind of person," John said. "Plus, I think she's been dropping a lot of hints to Mary since she found out we were engaged. Do you want to meet her - you know, before the wedding?"

Sherlock opened the fridge and deposited a half-empty milk bottle on the counter-top.

"Does she like solving crimes?"

"Not that she mentioned."

"Then probably not necessary," Sherlock said, pouring their tea.

John took the mug that was nudged in his direction, giving the milk a quick sniff before adding some to his tea. Somewhere in the course of the past ten minutes, Sherlock's whole demeanour seemed to have changed, but he was damned if he understood why. Maybe he should have been more encouraging about the Psychotic Wedding Wall of Baker Street.

When he looked up again, Sherlock was eating something. Something, John noticed, that he hadn't been offered.

"Is that flapjack?"

"Yup," Sherlock replied, still chewing. A small, flower-patterned Tupperware box sat on the counter behind him, a couple of pieces of flapjack still remaining.

"Did you make it?" John asked. "Because you probably shouldn't eat anything baked for you by a client. And if they came from Mrs Hudson, you should maybe ask first whether she made them for 'medicinal' purposes."

"They're perfectly fine," Sherlock replied, brushing oats from his hands. "An unexpected acquisition when I was out yesterday."

Nope, he still wasn't going to offer them around, the git.

"So, what's on the agenda this afternoon?" John asked. "More wedding...stuff? I can give you a hand if you like. Mary could come by after work; we could get a takeaway."

As he was finishing his sentence, Sherlock's phone vibrated on the kitchen table; Sherlock snatched up the device before John could see the name on the screen. As Sherlock's eyes rapidly scanned the message, his face started to break into a smile - the first genuine smile John had seen since he'd arrived. Whatever it was, it had to be at least an eight.

Almost immediately, Sherlock knocked back a deep swig of tea, dispatched the rest down the sink, and snatched up his jacket from the chair.

"Should I come?" John asked, mug poised in mid-air.

"Not necessary," Sherlock called, already in the hallway. "And I will almost certainly be engaged in an experiment for the rest of the afternoon and evening."

Now John couldn't help feeling sort of deflated himself.

"I could keep you company," he offered. "Update the blog maybe."

"Thank you, but no need," Sherlock replied, popping his head back around the kitchen door.

"Is...have you got someone coming over?" John ventured. He didn't want to rule out the implausible after all.

"No. Possibly. Probably not," Sherlock said, in rapid succession. "Do stay and finish your tea, though."

He disappeared back into the hallway.

"Oh," John said, now mostly to himself. "Thanks very much."

He was definitely going to eat at least two of those flapjacks the moment he heard the front door close. His gaze drifted from the Tupperware box to the table, where he noticed that something genuinely implausible seemed to have happened - in his haste, Sherlock had left his phone behind. John reached over to pick it up, and saw that the message that spurred Sherlock into action was still on the screen:

One liver ready for collection. Signs of mild cirrhosis, but otherwise a beaut - Mx

No sooner had John read the message than Sherlock burst back into the kitchen, swiping the phone out of John's hand and aiming a censuring frown at him before sweeping out again. After only a few seconds, Hurricane Holmes returned, this time snatching up the Tupperware box and murmuring something about eating the rest on the way and using the box later. He vanished again, and very soon John heard the sound of clattering size elevens on the staircase, which were quickly followed by the slam of the front door (and the familiar plea of "Sherlock!" from somewhere within Mrs Hudson's flat).

John sat staring at the doorway for a moment, feeling as though he was still playing catch-up. Obviously, Mary would be expecting a full report when he saw her later, and at this point, he honestly wasn't sure what to tell her. He was starting to think there was something else behind the sudden mania for wedding planning, but what was he missing? And then the sudden abandonment of that wedding mania in favour of Sherlock's more usual pursuits (if you could ever call experimentation on human livers 'usual').

Bereft of his intended snack - and unsure that he wanted to spend the afternoon in the shadow of the Wedding Wall - John got to his feet. As he was putting his jacket back on, his phone chirped with a text from Mary.

Hiya! How is he? xxx

John cocked his head to one side, beholding the splendour of the living room wall, and considered how best to respond.

Yeah, fine. He's got a new hobby - tell you later.

As he locked the front door of the flat, Mary responded.

Takeaway tonight? Just asked Molly, but she thinks she'll be busy. Might be a good sign? Xxx

Generally speaking, John tried to steer well clear of other people's relationship dramas, but he had to admit that a reconciliation between Molly and Tom would at least prevent Mary from worrying. He thunked down the stairs, reading Mary's follow-up text as he went:

Ask Sherlock about takeaway - tell him he can choose xxx

John stopped, feeling the frown lines form on his brow. He glanced back up to the door of 221B, and then back down to the front door. Thoughts still whirring, he typed a response.

He's busy tonight too.

Even as he sent the message, he could feel something needling at his brain. The questions about bridesmaids, the text about the liver, Sherlock's sudden change of plans, Molly's unavailability - all things that, on their own, were completely unremarkable. But…

No. Sherlock might accuse him of seeing without observing, but now he was going too far the other way - he was trying to make connections between things that weren't there. And he definitely wasn't going to mention this stuff to Mary, who was stressing enough about Molly as it was.

Or worse, if he told her, Mary might start on with her old 'theory' again, the one involving Tom's (admittedly marked) resemblance to Sherlock, and the way she reckoned Sherlock looked at Molly when he thought nobody was looking. God no. He'd heard enough about that to last a lifetime - and considering he and Mary were committing to a lifetime together, it was a subject best left alone.

His pocket vibrated with another text from Mary:

?! xxx

Oh God - it was starting already. Mary had taken the bait, and now John knew exactly how his evening was going to go, and no amount of smooth moves was going to change that.

As he pulled the door to 221 closed behind him, John had the distinct feeling that asking Molly Hooper to fill in for them on that investigation the other day had not been quite the innocuous solution they'd thought it would be.