This might not come as much of a surprise, given that he's a hyper-intelligent one-off with serious people issues, no respect for the personal and shockingly little understanding of how the world actually works, but Sherlock baffles me sometimes.

Sometimes it's a good thing. Say, for instance, oh, just hypothetically, we were tracking the movements of a suspect. Well, the client, actually, but a suspect, because… Do you know what? Long story. That's what we were doing.

And the whole case rested on what time this suspect left his girlfriend's flat last night. Now, last night, we'd been halfway across London chasing another lead that went absolutely nowhere. Naturally, I found this very frustrating, and even more so the fact that Sherlock just refused to be bothered in any way, shape or form.

As we turned onto the street where said flat might be found, I was telling him all this, hoping to get some reaction out of him.

I know. I'm an incurable optimist. It's a curse.

Anyway, he was still smiling. He, matter of fact, said, "But we know what time he left. Or, more accurately, we will in just a moment."

Like I said, this is the good baffling. He'd pulled something. He had something waiting, lined up. I don't know why I ever doubt, if I'm honest. For the sake of conversation, more than anything; if I ever do just eventually accept that he'll always have thought about it in advance, what'll be left to talk about.

"Go on, then. Tell me how."

He stopped at the place where the car had been parked, swept down and lifted a broken pocket watch from the gutter with a flourish. And me, I'm staring at it. Cracked glass…

"Placed beneath the front tyre, John. Broken at exactly the moment the car drove away."

Still staring, by the way. The case was all bent in at the back. The porcelain of the face had chipped…

"Oldest trick in the book, of course, but that's why nobody looks for it anymore. Nobody thinks. That's why the classics are classic."

One of the hands was still lying in the gutter. And a cog and a spring. I was picking them up, very quickly, looking about for any more, but it had been raining. These were just the things that had stuck in the mulch.

"John, what are you doing?"

"Where did you get that watch?"

And he knew what he'd done. It hadn't so much as fluttered on the edges of his mind until then, but the realization was sudden and perfect. He stuck his hands in his pockets, got evasive. "It was lying around the flat."

"It was in the drawer of my bedside cabinet!"

"You never carry it! Look at it, it's antiquated, why would you? It wasn't even wound when I found it, so clearly you don't use it, and I needed a watch so-"

"It belonged to my grandfather, Sherlock."

"…Ah."

I grabbed it down from his hand. The chain was still intact, but that was all. And at the back you could still see where my grandmother had it inscribed, though the message itself was unreadable.

The instant, visceral reaction? How quickly can I find another flat and where can I sleep in the meantime?

"John, I didn't know."

"All that means is you didn't look.

I took the pieces I had and left him standing there. That was last night. I think he stayed out to solve the case, because I didn't hear him come in. But when I get up he's sitting eating breakfast, just putting his phone down after sending a message. He says nothing, which is probably wise. I'm not sure I have anything to say back anyway.

I haven't really slept.

Part of me thinks this is stupid. Just because the watch has been destroyed doesn't mean the memory has gone with it, doesn't take anything away from what I have. I'll keep the pieces the same way I kept it whole.

The vast rest of me doesn't even want to think like that. That's his thinking. That the watch is just cheap sentimentality, and I'm almost overcome with the urge to find Adler's phone wherever he's hidden it and jump up and down on the bloody thing until it's nothing but tiny metal fragments and the memory of a horrible ringtone. That was my watch, and my memory and he had no right, none, and I'm damned if I'm going to rationalize it away for… for the sake of conversation over breakfast. No, no way.

So I eat, and in the same room as him, and I wait for an apology which probably isn't coming just so he'll know that I'm waiting. All through breakfast he curls farther and farther into himself, keeps his eyes down. God help me, I'm almost enjoying it. He should be ashamed, he should be guilty.

Then he gets a message back from the one he sent and jumps up from the table. "John, get dressed. Quick."

"…Excuse me?"

"Quickly. I'll get a cab sorted. And John? Bring the pieces."

Now, there have been those who have suggested, in the past, that I tend to blindly follow orders from Sherlock. That I trust him over much. And if I come totally clean, that could well be what happens here. I don't know why I do as he says. Whatever he has in mind, I have no desire to even leave the flat today. I'd like to stay in and be wilfully miserable for a while; I think it would help me feel better. And yet I get up, get dressed in a hurry and wrap the pieces in one of his handkerchiefs.

That's not petty, by the way. That's got nothing to do with the fact that he took something of mine for his own purposes without asking, or with me wanting some kind of terribly childish vengeance on him. And I swear I had nothing to do with what happened to his sock drawer, must have been Mrs Hudson.

He's already waiting in the back of the cab.

"Where are we going then?" and I try so hard not to sound remotely interested.

"To see Mag."

"Who?"

"Mag can fix it."

I open out the handkerchief under his nose. "I'm sorry, have you seen it?"

He doesn't look. His eyes flick down, but go back just as quickly. He just nods sternly to himself and says, "Mag can fix it."

Such a child. For one, I don't know who Mag is, but unless she has a time machine I'm not sure she can do anything for it. For another, even having the thing fixed isn't really going to solve the overall problem, is it? Making it like it never happened is not the same as making amends.

But I touch the beaten case of the watch and well, like I said, I'm an optimist. Let's see what Mag has to say first.

The cab pulls up outside the shop, and even an eternal optimist like me is having a very hard time being hopeful. It's a traditional, old-style pawnshop in a back alley of the East End, with chicken wire on one side of the window and an iron grille on the other, rows and rows of pads full of diamonds and gold jewellery. 'Bought and Sold' painted on the window above it all. Beyond that, only the dim insides of a shop that gets no natural light from the street.

The sign over the door says 'Archibald Slope and Son'. I'm wondering where Mag fits into that.

Inside, there are two women at the counter. One is skinny and blonde and looks barely out of her teens, writing in a ledger. The other is older, maybe older than me. Sits with her ankles crossed on the counter top and an eyeglass crunched between brow and cheek, studying diamond rings.

"Diamond," she says, and places one down on the countertop. "Zirconia," and throws it over her shoulder.

"Fake can be just as good, you know," Sherlock says.

Without looking up from a third ring, she says, "Not if you sell it for real, it's not. This, for instance, this here is a moissanite, and the little buggers will drive a careless pawnbroker out of business." She hands this last to the girl, takes her feet down and sits straight. She doesn't so much as look at Sherlock, but straight to me. Holds out an elegant, long-fingered hand. No rings, strangely enough. No bracelets. No watch.

"You must be Doctor Watson." Me, like a child with a broken toy, I place the little bundle in her palm. Her free hand takes mine very gently as she unwraps it. "What's Captain Caveman gone and done, my friend?"

A step behind me and knowing better than to say anything, Sherlock bristles. That's quite a nice feeling.

I don't know what else to say. "He broke it."

From studying the remains, she lifts her eyes to him, over my shoulder, "You're not wrong."

"There's an explanation, Mag-"

"The explanation being that you're a bloody philistine." She pops her eyeglass back into its crease and opens the case, very delicate, very precise. Hisses like a plumber. "Look, you know it's bad. You've got another gear or two missing, so I'll have to tear up a couple of donors. The face is a bitch of a repair and I need to find an hour hand that matches. But the case is intact. That can be beaten out. The glass isn't difficult to replace if you're not fussy about period-"

"-I'm not. I'm really not."

"-The movement's solid, nice make, so that'll come up fine once I get it sprung again… I'll refresh the inscription too, while I'm at it."

"You mean you can-?"

She's got warm eyes. The little hitch where she holds the eyeglass seems to stay in when she's not wearing it and makes her look ancient and wise. "Come back close of business tomorrow. I'll have him good as new for you."

And that's it. Aside from the other girl taking my number down at the back of the book, that's it. Before we're even gone, she's told the girl, Emily, to watch the shop, that she's not to be disturbed, and disappeared into a back room.

With Sherlock still that step behind, we walk back out into sunlight. "See?" he says. "I told you Mag could fix it."

This is that other problem. All the sweet relief that it's going to be fixed, going to be good as new, all of that goes away because he thinks Mag can fix it. And she can't. She can fix the watch. He knows lots of clever people with talents and skills, this is true. The watch will be fixed and that's wonderful. But this, it, the actual problem, that's not fixed. And there's no chance that it's going to be, because he doesn't even know it exists.

"I'm going out for the day," I say, turning in the opposite direction to him.

With confusion, wondering why we're not okay again, "John? But wh… where are you going?"

"I don't know. Don't worry about it. I'll probably stay at Mary's."

To himself more than me, softly, "Which one's that?"

Captain Caveman. Bloody philistine. To the list of known epithets I add my own; robot. Callous, heartless, thoughtless robot.

I don't much sleep. Again.

It's less about anger this time and more about the knot in my stomach. Thinking that somewhere out there the watch is getting fixed and Sherlock isn't. Sherlock doesn't know he's broken. Or if he does he doesn't care. Thinking through all the ways I could tell him, I can't find one that might work. Something that doesn't sound like it's beneath him, like I'm being irrational.

Which I am, by the way.

I've run away in order to better give him the cold shoulder rather than explaining the problem. I am defining irrational right now.

Morning comes and I try to distract myself until five o'clock. I try to read, try to go for a walk, try to leave Mary's place nice for her coming home from work.

I last until four. Then I make my way back to the pawnbrokers. I'm only forty minutes ahead of time. That's not bad going, is it?

The girl Emily is at the counter. At first it looks like she's hooked over the same ledger, but there's a copy of Heat magazine laid inside it, as I get closer. She looks up like I've caught her doing something horrible, closes it over and smiles. "You're early. Mag's not done. You're welcome to wait, though."

I thank her, and take a seat in a claw-footed armchair that's clearly been unsold a long time. In the interests of conversation, I ask if Mag is her mother.

"Near enough. I'm sort of… unofficially adopted." I pass the time getting her to tell me that her own mother 'ain't much interested', that she lives and works here, that she's kept by Mag and loves the life she lives very much. "It's good how it happened. Like how you just find people and it, like… even if it's not great to start off with, then-"

"Pardon?"

"Well, like, how I met Mag, innit? I was looking out for my big brother and his mate. They was both stoned off their heads and trying to rob the place and she caught me. But she never even give me over to the police or nothing. Says it don't matter to her 'cause she knows I'm alright, even if I was in the wrong. And then she goes and keeps me on." Then, while I'm still thinking about that, "How'd you meet Mr Holmes, then?"

Before I can tell her anything, the door of the back room opens. Beyond it, Mag, her chair leaning on its back legs, arced back; "Em, love, put the kettle on."

"'Course," she says. Looks at me. "You want a cuppa?" I accept the offer and she dashes off to the kettle.

And now that the door's open, I can hear that Mag's speaking to somebody. Now that Emily's out of the room I can listen in without seeming rude.

Mag saying, "Where were we?"

"I was a cruel, monstrous thing." Sherlock's voice. "But we'd been over it a couple of times, I think we've covered everything there. New topic. If I bring the links, will you put one back in my watch?"

"Putting weight on, love? You really must be clean. This Watson gent's good for you."

"Mag, he doesn't really know anything about that, I'd be much obliged if you-"

"In fairness, what does he know, when it comes to you?"

"That's hardly fair. You know nothing about it."

"I know he's moved his leather watch strap in a peg in the last year and you keep touching the former piercing at the top of your left ear, love, and that is all I need to know."

That could almost be him. It makes sense, I suppose, when you think about it. He knows a lot of things, certainly, but they don't just come to him, by osmosis. Somebody had to teach him the difference between diamond and moissanite.

For a long time nobody says anything. Or they say it so quietly that the distant kettle drowns them out. Sherlock's is the next voice I hear and it's strange, different. It's low and almost apologetic.

Don't look at me like that. I wouldn't say it if I couldn't hear it for myself.

"…Clean. Mag. I was clean and I just wanted to be… clean. From the start."

"Never occurred to you to come clean at all?"

"That's just a phrase."

"No it's not. Secrets are dirty, Sherlock. That's not just a phrase either."

"Just keep out of it."

"Oh, far be it from me to tell you what to do, love. You keep your secrets if you so please, and I'll keep them too."

"You don't have any of my secrets."

"I've got the one about the junkie and the pawnbroker, about how those two met and got to know each other. That one not a secret? Can I do what I want with that one?"

"…Stop it."

Suddenly I don't want to be listening in anymore. And I have to pretend I never was, because Emily comes back with the tea. Three mugs. One for me. One she leaves on the counter for herself. One she brings to the other door, and when Mag cheerfully takes it off her, she closes it right over.

"You alright, Doctor Watson?" Emily says. "You look awful white."

"I'm fine."

He must have gone out a back door.

At five-to-five, Sherlock edges in from the street. Stands that full step behind me again, doesn't say so much as hello. Just hovers there. Waiting to be forgiven, to be invited. It's not because I want him to suffer that I keep my mouth shut; it's because I don't know what to say.

At five exactly, Emily comes out to lock the door. She's in the middle of that, the church clocks couldn't have finished striking, when the back room door opens again. Mag looks exhausted, squinting, but she smiles. Waves me forward to the counter. She leaves the watch there and steps back, falls into her chair and picks up the end of Emily's tea. Relaxes away from me.

I go tentatively to the watch. Pick it up by the chain. The gold shines, all the scratches buffed away, the body pushed back into its perfect curves. She matched the hands. She wound it and it ticks towards five-oh-one. The inscription is legible and elegant again.

The crack in the face has been sealed in new enamel, and the numbers painstakingly painted in.

"It's perfect," I say.

And Sherlock, who has been watching cautiously over my shoulder, tries to cut in; "You've outdone your-"

"Ah, ah!" Mag raises one hand, flattened; 'stop'. "You are not to speak. That watch survived Afghanistan and nearly didn't survive you."

He retreats.

I look up, "What do I owe you?"

"You, my friend?" She takes my hand again, pats the back of it. "Nothing." Then cuts her eyes at Sherlock, "Him, on the other hand, he knows exactly what I expect of him, don't you?"

Sherlock doesn't answer her. He shoves his hands in his pockets, turns on his heel and shoulders his way out the door. Mag wraps the watch up in the same handkerchief I brought it in, presses it into my hand. "Be kind with him," she says, "He's never had what you're holding."

"What, a heart?" I say. I don't mean it. Just getting it off my chest.

"Someone else's," she replies. Then nods me out after him.

Sherlock is standing a few steps down the street. Hands still in his pockets, but if you look closely you can see his fingers twitching back on themselves, the way they do when he wants a cigarette. I stand next to him, looking past him, down the street. Just as a start, just as a greeting, "Alright?"

"John, I'm sorry." He says it very quickly, as if it pains him to say it and, more than that, as if it's pained him to keep it in this long.

"Yeah, well… it's fixed now, anyway."