Landing at Heathrow, he stops to check the local news. Sits a long moment with his phone, looking for the telltale signs, the keywords. He keeps seeing them. He's been seeing them all over the world. Whether he goes, whatever he does to eradicate them, they're still there. 'Mysterious', 'no suspects', 'police stumped'. Perfect crimes. And not just perfect, but Moriarty. Denver to Dubai, his perfectly formed games are still playing out. It's not right, not anymore. For some short period after the death, yes, maybe, there could still have been orders to follow. But they've been dead now, both of them, more than two years.

And Holmes is so bloody sick of arriving that one day too late. After the murder, after the heist, after the kidnapping. There to solve it all, yes, but one chapter at a time, game by game. It's not enough. In two years, there have been eighty-two cases. Seventy arrests, twelve deaths; every case solved. And the army seems no weaker now that it did on the first day.

At night, he sweats and tosses in dreams of the hydra, where every head he cuts away grows another three still more vicious. His only respite is in imagining the creature's heart still beating in his hand, and the heads all falling suddenly still.

But maybe he's been on his own too long.

He's incognito as he leaves the airport, dressed in jeans and suit jacket, coolly casual, unquestionable. Whilst on his travels he's been told he makes a convincing blonde. It's strange to adopt the disguise again; he's been out of Europe, beyond the reach of the sort of press that would recognize him. But to be discovered in England, it's unthinkable. Not before he's ready to be, anyway. And he will be. He will. He's coming back, and he silently promises that to memories of faces he has not allowed to fade. He made that promise the day he walked away, and meant it, and still means it. He's coming back. But not until it's over.

All the paper trails to dummy accounts, all the disconnected phone numbers, every dead end that had been so frustrating coalesced just three weeks ago, in a small cafe in Sydney, and led him to a complete and perfect conclusion.

Firstly, that there are still orders travelling through Moriarty's organization. From how many voices and how they have kept up the run of beautiful crimes, he doesn't know yet.

Secondly, that all those voices are still based in London.

An army is only as good as its generals. He'll have them. He was a fool in the beginning, not to see that this is the only logical course of action, and arrogant to think that he had been so effective in removing the root cause.

He thinks again of that beating heart and knows the address to give the cabbie.

Holmes always sits in the front of taxis now. It means enduring an added brace of mindless chit-chat, but it lets him keep an eye on just who's driving. Cabbies have proven to be a dangerous crowd in the past. Anyway tonight, for once, mindless chit-chat isn't such a pain. He hasn't been doing an awful lot of talking, hasn't heard an awful lot of people talking to him. He makes enough assenting noises to let the driver continue all the way into the city.

Then the streets start to look dimly familiar, like the first few bars of a song on the radio, before you can place the words. It falls over him and balls up, a real, physical pain, just beneath his ribs. His throat knots and the temptation to have the taxi turn around, get away, just skip this part entirely, it's big. It's overwhelming, almost impossible, except that he can't speak to give the order. Instead, the driver lets him out at the appointed corner and Holmes pays his fare.

He walks another two streets, climbs the steps to the right door and knocks. Timidly at first, then stronger.

Waiting for an answer, a scream makes him seize and turn back towards the street. But it's not a scream of fear or pain. It's a teenager, no more than a girl really, crying out with something primal, firing down the middle of a road on a pair of rollerblades. She flashes in and out under the streetlights, crying, "Yes! Yes, fucking A!" And then she's gone, down the street and round the corner.

The door opens and Holmes forgets her. He turns back.

Molly Hooper stands in the doorway, looking tired and put out. Wearing running shorts and holding a hooded sweater tight across her stomach, and grey fur slippers with rabbit ears. And maybe he's never seen her like this before, but he knows this is the same as ever. She hasn't changed and that's enough for now.

"Can I help you?" she mutters irritably. Then, slowly, recognizes him. "Oh. Sherlock." The sound of his real name is forgotten, unfamiliar. You've gotten tan..."

He stands mute, dazed. He's forgotten what to say, until he finds she's still looking him over. Instinctively, "What? What is it?"

She launches forward, wraps her arms around him so quick and so tight he stops breathing for a moment. Very quickly, he gets over being stunned and raises one tentative hand to pat her back. That's all it takes; Molly remembers herself and stands away, pulling him inside instead. "Sorry. It's just... you've been gone so long, and then you stopped calling and I thought..."

"Dental records, Molly. They would have caught me if I was dead."

"I thought of that. I even tried believing it for a while." He flounders, trying to remember how to say sorry. She sees it before he can quite get there. "Come on," she says, "Come and sit down. I'll put the kettle on. I want you to tell me everything."

No. That's not a good idea. He lets her make tea, he even helps, he sits down with her in the living room with the television on mute and lets the warmth and normality sooth him for a blissful hour, but tell her everything? No. He tells her parts, little stories that will amuse her or explain him, enough to deaden her curiosity, but not everything. Softly, in stilted little phrases like one that has just recently learned the language, he tells her just enough to keep her from asking anymore.

At the end of that hour a low, fearful silence falls. Molly starts to lean towards him, then closes her eyes and falls away. "You're not really back yet, are you?"

"No." And he's remembered now and so adds, "I'm sorry. I didn't want to see you again until everything was ready."

"You can't keep putting me in this position, Sherlock, it's not fair."

"I know. I'm sorry." He's really on a roll now, he thinks darkly, and better stop, because there's a whole road there if he starts apologizing to people and he might never see the end of it if he begins.

"Why are you really here?" she says. She's a little warier now, a little more distant and he really is sorry for her and sorry for everything. But she's asked him a question and he has to answer.

He tells her everything about this latest part, about the voices still calling out to the world, the generals. The hydra and the heart, he only just manages to keep to himself. He wants to tell her that. He wants her to tell him that doesn't matter, that's all normal and fine and alright and he's not losing his mind. But he keeps his monsters to himself. "And I suppose, Molly," he ends, "What I want to know, why I'm really here is... Can I still depend on you?"

"You know the answer to that," she says, "or you wouldn't have come."

"But I need to hear you say it."

"Of course you can."

Relief is sudden and new as a religious conversion, all answers and light and the pressure falling away. But he hasn't quite made it as far as 'thank you' in his remembering. Instead he reaches out and puts his hand over hers, before he starts to get up.

"You're going already?"

"Need to find somewhere to stay."

"You can stay here."

There's a twitch, the long lost ghost of how to smile. "No. Dangerous."

"Oh. Of course. I'm a... what did you call it before... a 'known factor', wasn't it?" He winces to have it brought up again. Their last parting wasn't exactly relaxed. She had wanted to come with him. And back then, when he still had the words to do it, he'd spun excuses and logic until she was all caught up and spun right along with him. But she's had time now to dissect all of that. She knows now; all he was really saying was that he wouldn't see her hurt. This time, when she sees him to the door, she isn't looking up. Last time she looked up, big, hopeful eyes sending him off, wishing him well. This time, she looks down at their feet and she nods. Says earnestly, "Whatever you need, Sherlock. Whatever brings you back."

He's still not quite up to speed on gratitude. He turns away from her and waits for the door to close. That's a bit easier. He knows what that sound is like.

He determines to walk, all night if he has to, down into the darkest part of the city and find, like he usually does, the lowest possible dive, curl up and make ready for what's coming.

He gets as far as the end of the street.

Then the scream again, the girl coming back this way, firing down the footpath at full pelt. When she reaches lamppost near the corner she grabs hold of it and swings right off her feet, right into him. "Look at you!" she cries, "Goldilocks!" For just a moment too long, she's all over him, hands straightening his lapels, patting down his pockets. He takes her for a thief, a pickpocket and takes her by the wrist. He twists her arm up behind her, but she shoots both feet forward off her wheels and he has to let go or break the bone. "Alright, alright, calm yourself! I come in peace." He doesn't like that, doesn't like the sound of it. He starts looking about, up and down the road. "Don't look for a cab," she laughs, skating a few circles around him, an arabesque into the street, "there aren't any, not for ages all around. They're all off into the wild blue yonder, carrying nothing but ghosts and all my money."

"You sent them away."

"No flies on the detective!"

"Why?"

She stops dead, skates up and stands toe to toe with him. This stranger looks up, and her eyes are big and glittering. Strangely, though, there's no hope there, nothing of the sort. "Because I want to walk with you," she grins. "Would that be alright?"

So he begins to walk again, and she falls into step in long glides. It gives him a chance to take her in, to notice something other than the demonic eyes and smile. Skinny, malnourished. Dirty. What he originally took to be roller blades are just old skates, too small, strapped to her beaten trainers. A long, greasy ginger ponytail and worn-out clothes. Homeless. She's unusually quiet while he notes these facts and draws his conclusion. "You don't remember me, do you?"

"No." But then, he doesn't remember a lot of things. Maybe she'll come back. 'Sorry' came back pretty sharp.

"Good," she says. "But I remember you. You'll have to do more than get a bit of colour to fool me, sunshine." She stops to giggle at her own joke, dancing backward in front of him, keeping distance as certainly and effectively as the end of a treadmill. All of her still holds that desperate, terrifying glitter, like a thing about to drag him into the abyss. He could almost smile at that, when she's so much too late to claim that honour. "You have no idea how long I've been waiting for this."

"Bit more than two years?"

"Yeah, but how long it feels."

"I think you'd still be surprised."

"Maybe I would." She giggles again and goes ahead of him, speeding along, doubling back. Screams out a poem with madness and animal joy. "M is for Molly, who was washed out to sea, who thought she was forgotten, but never was by me." On the far corner, she stops, with another street lamp for her spotlight, throws her head back and screams, "S is for Sherlock!"

Before she can go on, he's with her again, grabbing her back into the hedge with a hand over her mouth. Behind it, she's still laughing. She bites, and when he lets go, giggles, "Don't worry, they'll just think I'm a believer. Not a trace of doubt in my mind... You ruined my little verse, should I start again?"

"Kindly don't. Now who are and what do you want?"

"Neither of those questions, nor the answers to them, serves you in the slightest. Next time we meet maybe you'll know what to ask."

"Next time?"

"Of course there'll be a next time. You're not just going to walk off into the sunset after me giving you presents and everything, are you?" His reaction is just a millisecond too slow. In the gap, she's out of his grasp and into the street again. After putting a little distance between them, she stops and backs away slowly, shadow-boxing. "Ladies and gentlemen," she declares to the street, as all her screaming and cackling brings lights on and doors open, "all bets are off. Seconds out, round... three, is this? The fight of the century is back in business. Yes!" She screams off into the distance, and leaves Holmes no choice but to stay in the shadow of the hedge until doors start closing again. He watches after the demon and flinches when a soft hand falls lightly on his shoulder. He spins on his heel, but it's Molly. Running shorts gathering at the waistband of her jeans, tugged on in haste, the rhythms of her speech slightly altered; she came running. "What's going on? I heard someone shouting-"

"I know. Go home. I'll call."

That's all he can say. She pulls back, looks almost hurt. She doesn't say goodbye, doesn't wish him luck, doesn't ask if he's sure, but turns away and goes back the way she came. It was cold of him, he knows that, but he doesn't know yet what those presents are. He wants her far from him. And by the time she's gone, the grumbling husbands and housewives, the young professionals and the kids with their morbid interest, have all given up and gone back inside. There in the street he pulls off his jacket. That's what she was doing. When she first landed on him, when she was all over, he thought she was taking something. She wasn't. She left a present in every pocket. In the inside is an elegant switchblade knife. A brave gift to give in the middle of an assault, he thinks, summoning some of the old eloquence.

In the left side, a single playing card, a joker.

In the right, a four card draw. Jack of Clubs, Queen of Hearts, King of Diamonds, Ace of Spades.

In the breast pocket, next to his own, a mobile phone. Two new messages. The first is a picture of the hand he's just been dealt, laid on green baize, exactly as it is. The second, the address of the lowest sort of dive, a room number and one line of text – 'You're booked in under Smith.'

It all has a very familiar feel.

'Round three,' the messenger said.

Never before has it been so patently a game.

Never before has he been so very willing to enter play.