A/N: For hitlikehammers.

Thanks to blue_eyed_1987for beta!

Chapter 1

Everybody knows
death creeps in slow
Til you feel safe in his arms
(from O Maria by Beck)

Sherlock pauses for a moment to catch his breath. This tree is much bigger than the ones in his garden – he's so high up now that the picnic cloth looks like a handkerchief spread out on the ground. Sherlock can pick out the yellow coloured dot that is Mummy's head, bobbing up and down as she laughs. The small dark splodge beside her is Mycroft, of course. He's pretending to read a book but Sherlock knows he's actually eavesdropping on the grownups. The high-pitched tone with which Mycroft had hissed at him, go away Sherlock, I'm busy definitely meant he was trying to be subtle.

Sherlock can't understand what Mycroft finds so interesting – they're all just talking about politics and University regulations and sexual innuendo. Playing pirates is much more fun.

Sherlock plucks an acorn off the branch beside him. The picnic party, he decides, is an enemy ship, skulking in green waters. He's climbed the crow's nest to spy on them – underneath him his crew is hidden by the bristling leaves.

"Fire at will!" Sherlock calls out and launches the acorn towards the picnic blanket. It lands a long way short, but Sherlock catches Mycroft's head lift up and look at the place where it fell. Sherlock looks around him for more ammunition. There isn't anything close by but at the end of the branch is a tempting little clutch of acorns.

Sherlock gets to his feet and steps out carefully onto the branch. It creaks under him, the leaves at the end of it shivering. Sherlock pauses, wondering if perhaps he ought to try another branch instead, when he hears a rustle of feathers.

The bird whooshes over his head and lands on the end of the branch. It's a starling – Sherlock can tell from the spattering of white speckles on the oily black feathers. There's something wrong with the bird's tail, the feathers crumpled, standing up at an odd angle as if something had tried to take a bite out of it. Sherlock thinks he can see the white gleam of bone poking through. If he gets a closer look perhaps he will be able to tell what sort of animal had wounded it – maybe there will be teeth marks. Sherlock gets to his knees and crawls closer down the branch. The bird cocks its head and looks at him.

That's when Sherlock catches sight of something very odd out of the corner of his eye – a flash of grey moving over the green grass below him. He looks down.

There is a boy standing directly beneath him at the foot of the tree, looking up at Sherlock. Sherlock stares. The boy seems like an ordinary child except he's the wrong colour. From his eyes, to his upturned nose, to his clothes – he's all grey, as if he's been painted with clay.

The boy bites his lip and then holds up his hands towards Sherlock, palms open, as if he's waiting to catch him. Sherlock opens his mouth to ask what the boy is doing but before he can get a word out he hears a sharp cracking sound and the branch beneath him gives way. He crashes into the branch beneath him, which knocks the breath out of him, and after a moment of hanging in dizzyingly empty space he slips backwards.

The next thing Sherlock is aware of is that there is a circle of faces looking down at him. Mummy is next to him, wringing her hands and talking rapidly. On the other side of him the little grey boy kneels in the grass, watching him.

"Wha-" Sherlock starts to say, but finds he can't draw in enough breath to finish the world. Pain stabs through him, as he tries to pull air into his burning lungs. He can feel a terrible pressure growing on his chest, as if he is being crushed by a great weight but he can't see anything on him. He tries to roll onto this side and sit up, but the pressing feeling only grows worse when he tries to move.

"Darling," Mummy says, smoothing his hair. "Don't try to move. Just lie still, help is coming and Mummy's here."

Sherlock glances back at the boy. He looks very sad, Sherlock thinks, mouth pulled downwards, small forehead creased in serious lines. Despite the graveness of his expression, Sherlock likes looking at him. There's something comfortable about his face, something that makes Sherlock feel warm deep inside, peaceful, the pain in his chest seeming to ebb away. He's never liked to be still but right now he's starting to think that lying here and doing nothing at all might be a very nice way to spend time after all.

"Sherlock, please, stay with Mummy, stay with me….." Mummy keeps talking and talking but Sherlock finds it increasingly difficult to understand the words coming out of her mouth. Her face is a blur.

The boy, on the other hand, seems to be getting clearer and clearer, as Sherlock were turning the adjustment on his microscope to focus on his face. Now he can see the faint freckles on the boy's nose, the slight crease between his eyebrows when he frowns. The single strands of hair hanging down over his forehead stand out so sharply Sherlock thinks he could count them. He can hear the boy's breath in his ears.

The boy ducks his head a little and sighs deeply, small chest rising and falling, before reaching out a hand to hover over Sherlock's cheek.

A harsh sound breaks through the hush, a discordant whooping and screeching that makes Sherlock wince. Dark shapes approach, circling around him and the grey boy before descending on Sherlock and pushing something cold and hard over his mouth and nose. Suddenly Sherlock remembers the pain from where he'd hit the branch and agony explodes through him again, so blindingly sharp that for a few minutes everything is blotted out by it.

The next thing Sherlock knows he is being carried on a long bed through the field. Up close Sherlock can see the dark shapes are men wearing paramedic uniforms and that one of them is talking to Sherlock is that carefully kind tone adults always use with Sherlock before they've had a chance to get to know him better. Mummy is running beside them, her face very white and pinched. Sherlock raises his head a little. The grey boy is also jogging after the stretcher but the medics are too fast for him - he's losing ground, slipping further and further away until Sherlock blinks and can't see him anymore.

Hospital is very boring. Sherlock is told over and over that he is Very Lucky. He's broken his leg and broken his ribs and had a tension pneumothorax where a piece of bone punctured his lung, but he'll get completely better with time. Sherlock isn't sure why they keep telling him the same thing, but remembers Mycroft telling him that adults like repetition and that it's best to humour them. It isn't like he has much choice - his chest is so achey and tight that he can't talk back.

Mummy stays with him overnight. Sherlock can't sleep in the horrible plastic-smelling hospital bed, so Mummy reads him stories until her voice becomes as scratchy and hoarse as Sherlock's.

Daddy and Mycroft arrive in the morning. Daddy gives him a long and very careful hug before Mycroft pushes him out of the way.

Mycroft's face is pale, chubby hands clenched into fists. "Are you stupid?" he asks Sherlock.

"Mycroft…" Mummy says admonishingly.

"There are twelve different ways to tell is a branch is strong enough to support your weight. Twelve. I told you to memorise them. Did you not remember? Or did you just fail to apply them?"

"Now, now. I'm sure Sherlock just.." Daddy begins but Mycroft ignores him.

"Climbing trees is a childish game anyway. I grew out of it when I was five. You're almost seven. I don't understand how I can be related to someone so backward!"

"Mycroft!" Mummy repeats, and Daddy puts a firm hand on Mycroft's shoulder, leading him over to a chair, muttering something in his ear.

Sherlock's hands curl into fists. He wants to shout back at Mycroft but just thinking about the effort involved makes his chest hurt a lot. Mummy pulls a silly face at him behind Mycroft's back which makes him feel a bit calmer. Mycroft doesn't know everything.

Speaking of which….

"What …happened… to the little boy?" Sherlock asks, ignoring the stabbing pains in his chest.

"What little boy?" says Mummy.

"There was a boy….under the tree… painted in grey. He was trying…. to catch me."

Mycroft turns away from Daddy to stare at Sherlock, eyebrows rising towards his hairline. He turns to Mummy.

"Mummy," he says loudly. "I think Sherlock is broken."

"Of course he isn't." Mummy says firmly. "But you know, darling, there weren't any other children at the picnic. Just you and Mycroft."

"He was there," Sherlock insists, and tries to sit up before being reminded of how broken his chest is. "I saw him."

"Oh, well, maybe someone was just passing by," Mummy says. "We might have missed him in the confusion, mightn't we Mycroft?"

Mycroft rolls his eyes as if to say he'd done no such thing. Mummy smiles down at him, but it's the same too-wide smile she'd used when telling him about Father Christmas so Sherlock knows she doesn't really believe him. It doesn't matter, Sherlock decides. He'll find the grey boy again himself, and then they'll all know the truth.

Sherlock returns home soon afterwards but is mostly confined to bed or sitting around in his chair. His plastered leg won't let him go and investigate the boy he'd seen under the tree – it won't let him do anything interesting at all. Even looking at samples on his microscope is impossible because his chest hurts when he leans forward.

It isn't as if his family doesn't try to entertain him. Mummy chatters to him about her research and sets him equations to solve, and Daddy plays him piano. Mycroft, with a pinched and long suffering expression, reads to him from the books Mummy has brought home from the library. Sherlock doesn't particularly like it when Mycroft reads, because he always sounds sarcastic and refuses to do any of the character's voices, but it is better than nothing.

"He was a very silent man by custom. All day he hung round the cove or upon the cliffs, with a brass telescope; all evening he sat in a corner of the parlour next the fire and drank rum and water very strong. Mostly he would not speak when spoken to; only look up sudden and fierce, and blow through his nose like a fog-horn; and we and the people who came about our house soon learned to let him be. Every day, when he came back from his stroll, he would ask if any seafaring men had gone by along the road? At first we thought it was the want of company of his own kind that made him ask this question; but at last we began to see he was desirous to avoid them." Mycroft reads nasally, as Sherlock shifts to look at the words over his shoulder.

"Oh," says Sherlock says.

"What is it?" Mycroft says, looking irritated at the interruption.

"Give me that book," Sherlock says. Mycroft hands it over with raised eyebrows and Sherlock stares at the picture on the page. The man with the peg leg and patch is clearly the seafarer and secret pirate (obvious) that the narrative was describing but Sherlock's eyes are drawn to the boy beside him. Small, with large blue eyes and a tippy-up nose. On closer inspection the resemblance isn't as strong as Sherlock had thought, but none the less it is enough to give Sherlock pause. The memory of the grey boy had been slipping away from him, like ice melting to nothing in his palm. The illustration makes image of him trickle back through his mind. He looks at the caption under the illustration. Jim Hawkins. Jim doesn't fit right somehow in Sherlock's head. He tries again. Jim. Jimmy. James.

"Sherlock?" Mycroft says, and Sherlock turns back to scowl at him.

"You can carry on reading," Sherlock says imperiously. He waits until Mycroft has gone to the loo to surreptitiously tear out the page with the picture of Jim Hawkins on it, fold it up and tuck it into his pocket. When Mycroft comes back and picks the book up again he gives Sherlock a very strange look but says nothing.

It takes two months before Sherlock can limp out across the field on his crutches to the field where the picnic had happened. There is no one there, of course. Sherlock examines the grass under the tree carefully where he had fallen and where the boy must have stood, but of course there are no clues to be found. Sherlock thinks about the past two months and how often it must have rained and how the grass must have grown. He wonders how long it takes for footprints to be obscured under normal weather conditions and decides he will make a study of it one day.

Sherlock stands and listens for a moment to the wind rustling the leaves on the tree and the distant sound of sheep bleating.

"Hello," he says. There's no response. "Grey boy? Jim? James?"

Nothing. The air around Sherlock feels as balmy and indifferent as anywhere else. Sherlock bites his lip in frustration for a moment and turns away.

It's a year before Sherlock stops carrying the picture of Jim Hawkins around in his pocket and another three years before he stops making the hopeful pilgrimages to the tree. By the time Sherlock is old enough to go to school the memory has been, if not forgotten, pushed to the back of Sherlock's memory, to a quiet undisturbed corner where it gathers dust.

Then, when Sherlock is twenty years old, he sees the grey boy again.

Sherlock is lying flat on his back on the floor of his room. He has made an error of judgement. His heart is skittering in an uneven rhythm in his chest, and Sherlock can hear the beating of his own blood throbbing painfully through his veins. Above him the lights seems to fizzle and crack.

An overdose, Sherlock thinks, is a pitifully ordinary way to die. Still. At least he won't be bored for long.

It's then that Sherlock hears something close to his ear, a soft exhale of breath. Since he is, to the best of his knowledge, alone in the room, this is something of a puzzle. Carefully, painfully, Sherlock turns his head to look.

"Oh," he says. "It's you."

The grey boy isn't a boy anymore, but a young man – taller (but clearly still not very tall), face filled out but with the same unmistakeable upturned nose and smooth looking grey-washed skin. He's lying on the floor beside Sherlock, turned on one side. Their faces are level, and Sherlock feels caught by the clear softness of his gaze, pale grey flecked with black. Curious, Sherlock raises a hand, reaching to touch but the grey man shakes his head infinitesimally.

"Phone," he says. His voice is very quiet, muffled as if he were on the other side of a wall rather than inches away from Sherlock's face.

"What?"

The man's eyes turn to something behind Sherlock and Sherlock struggles onto his elbows to look. The room phone sits on the desk a few feet away.

"Too far," Sherlock says, and the man's expression shifts, jaw tightening and eyes glistening in a way that looks like pleading. Sherlock isn't much given to acts of compassion for strangers, but Sherlock finds he doesn't like seeing the look of distress on the grey man's face. Despite himself, Sherlock finds himself hauling himself up and over to the desk. He knocks the phone out of its cradle and with shaking fingers dials 999.

"There," says Sherlock thickly turning back to where the grey man had lain. "I hope you're ha-"

But the floor is empty. The grey man has disappeared. Sherlock falls back, listening to the thundering of his blood and the gabbling of the operator on the other end of the phone and curses himself for losing his grey man again.

He doesn't mention the grey man to anyone at the hospital – at best it will lead to a lecture about the dangers of abusing hallucinogenics, at worst it'll result in an admission to the psych ward. And he isn't a child anymore – he isn't naïve enough to share his reality and expect people to understand.

It isn't the drug, of course. Sherlock is sure of that, but decides to prove the matter empirically just to be sure. He runs various experiments, altering his position in the room, the quality of light, amount of sleep, diet, the dosage of the drug – but fails to summon so much as a shadow of a grey person.

Eventually Mycroft appears with the intention of interrupting his experiments and taking him into rehab. Evading him takes up so much of Sherlock's time and energy that it leaves room for little else. And then, one fateful evening, when he is in the act of giving Mycroft's minions the slip, he happens to find himself at the scene of a grisly murder and develops a new preoccupation entirely.

Sherlock is twenty nine years old when he sees the grey man for the third time. The cat burglar he's been chasing turns out not only to be more agile than Sherlock had anticipated but also carrying a concealed knife. Sherlock registers this fact at about the same time as he staggers backward in the alleyway, sliding down the wall. The wound on his thigh spatters a disturbing quantity of blood the floor. Sherlock gropes at the scarf around his neck, tugging it loose, as spots begin to dance in his vision. He is in the act of tying it around his thigh, a rather inadequate tourniquet, when he hears footsteps and looks up. The grey man stands for a moment looking down at Sherlock before crouching down in front of him. His face is thinner than when Sherlock last saw him, thin lines appearing on his forehead. He looks down at Sherlock's leg with something like resignation. Sherlock pulls at the scarf but his hands are starting to feel numb, the alleyway around him blurring.

"Tighter," says the grey man, in that same muffled distant-sounding voice.

"You could help," Sherlock gasps out, but the grey man only looks at him and slowly shakes his head.

"I'm dying," says Sherlock. "Aren't I? That's why you've come."

"Stop talking," the man says. "Tighter."

"That's why you always come," Sherlock says, rather pleased at such deductive brilliance in the face of what is probably massive blood loss. "When I'm…. on my way out. What are you, my guardian angel?"

The man glances up at him and a complicated sort of expression flashes across the man's face. He takes a short breath, and then lets it out. Sherlock feels the stream of air on his face.

"What are you?" he repeats. "James?" he tries out, but the man only stares at him gravely.

"Pull," he says. "30 seconds."

Sherlock hears the tell-tale wail of sirens in the distance, and sees the man rise and take a short step back.

"Don't," he says. "Don't go."

But the man only gives him a sad half-smile and takes another step away from him. Sherlock hears footsteps at the other side of the alley, the unmistakeable banging and fumbling of approaching paramedics. When he looks back to the place where the grey man had stood, he is gone.

Lestrade visits him in hospital a few hours later, looking harried. Sherlock observes him fidgeting at the foot of his bed through his opiate induced haze.

"I thought you'd want to know, we caught him."

"James?" Sherlock says, somehow aware that this option doesn't make sense but also unable to put his finger on why.

Lestrade blinks several times. "No – Asquith Fortender. The man who stabbed you."

"Oh, yes," Sherlock says. "Harder to catch a grey man. Tends to slip away just when you think you've got him."

Lestrade's eyebrows rise and he goes to take a frowning look at Sherlock's morphine pump. "Do they know you're an addict in here?"

"The drugs are entirely necessary." Sherlock says.

"I've heard that one before," Lestrade mutters.

"Someone has ripped a hole through my leg."

"Yeah," Lestrade says, and he looks a bit softer after that, eyes crinkling up in the same way the grey man's had. James. James, James. James? The name itself frustrates Sherlock – he has the sensation of nearly reaching a realisation only to have it wriggle out of his grip at the last moment

"I'll need time off," Sherlock says. "Won't be able to take cases for a while."

"Yeah, I thought you would," Lestrade says, looking down at Sherlock's bandaged leg.

"I need to do research," Sherlock says. "Lots and lots of research. You'll have to bring me my laptop. My keys are in my coat."

"Sherlock – I've got a job, I can't be running back and forth after you. Isn't anyone else you can ask?"

Sherlock fixes him with a piteous look of the sort he'd spent years perfecting in the mirror for occasions such as these. Lestrade sighs, and rubs a hand through his hair.

"Fine. Laptop. Anything else you need while I'm there?"

Sherlock beams at him. "I'll make you a list."

Sherlock is determined not to let the mystery of the grey man evade him one more time, but researching the matter proves more difficult than he'd hoped. He is forced to resort to the extreme measure of joining message boards frequented by ghost hunters, angel worshippers and spiritualists of various descriptions. It takes several weeks trawling through the ramblings of the delusional and the gullible before he finds something could be a lead. Or, more to the point, someone.

It has been a while since Sherlock has visited St Bart's hospital. The smell of corridors near the morgue is surprisingly comforting – cleaning fluid, antiseptic, formaldehyde. Eau de autopsy. Sherlock lingers in the corridor near the registrar's office, waiting.

It is only ten minutes before the registrar appears bustling out of the door with her lab coat flapping at her heels, her arms full of files. Sherlock springs to attention, deliberately stepping into her path.

"Excuse me,"

"Oh!" The woman starts and, as Sherlock predicted, the files tumble out of her arms onto the floor, paper spilling everywhere.

"Oh, gosh, I'm terribly sorry," Sherlock says. "Please let me help."

"Oh, no really, it's-"

"I insist," Sherlock gives the woman his most winning smile, and notes with satisfaction a blush flaming across her cheeks. He sorts the paper swiftly and efficiently, stacking the files again and handing them to the woman.

"Thank you, goodness you are awfully fast! I mean – oh, that sounded wrong. It always takes me ages to do that sort of thing and I-" the woman babbles.

"It's not a problem," Sherlock says, and looks down at her with the attentive focus that he knows people find attractive. "I don't think we've been introduced, have we? My name's Sherlock Holmes, new consultant in Paediatrics."

"Molly Hooper," says Molly.

"Molly," Sherlock repeats, in a deliberately caressing tone and pauses for a moment. The woman looks up at him, eyes wide and – yes – pupils just slightly dilated. Sherlock bites his lip a little in a parody of hesitancy.

"Listen – I know it's terribly forward of me but - would you fancy grabbing a coffee later?"

The woman's blush deepens and for a moment Sherlock wonders if she is going to spill the files again – to her credit she does not. "I'd like that," she says. "I'm on the staff list, just give me a text."

Sherlock does not, in fact, have a copy of the staff list, not being a St Barts employee. He does, however, already have Molly Hooper's number.

They arrange to meet in a café claiming to be an American-style diner down the road. Sherlock chooses it because it has large high backed leather booths rather than seats, giving them a little privacy. (If the content of the conversation he is about to have ever gets back to Mycroft he will never hear the end of it.)

Molly arrives two minutes late, looking pink and flustered but with a broad smile on her face. As she glances at the booth Sherlock notices her smile falter, a frown line appearing on her forehead.

She must have seen through his pretence somehow. Well, that will save time. At least she hasn't immediately stormed out.

"Can I get you-all something?" A waitress, making a very poor attempt at imitating a midwestern American accent, appears at their booth.

"I'll have a black coffee," Sherlock says.

"Um… tea please," Molly says. Sherlock waits until the waitress has brought their drinks, before leaning forward and beginning.

"I'm afraid," he says. "That I asked you here under false pretences, Molly. Or should I say Mystic Mary."

Molly looks up at him, looking startled. Then she groans.

"Oh God, not again. How did you track me down?"

"With some difficulty," Sherlock admits. "You've changed your name twice since your days on the stage and changed address four times. But there are always ways."

"Then you realise, I don't do this sort of thing anymore," Molly gets up and fumbling in her purse pulls out a couple of pounds which she slams down on the table. "Goodbye."

"Wait," Sherlock catches her by the wrist. "Please just give me ten minutes. I really need your help. There isn't anyone else I can ask."

"Let go of me," Molly says.

Sherlock drops her hand immediately but continues looking up at her with his best pleading expression. It seems to work – there is a look of pity dawning in Molly's eyes when slowly she lowers herself back into her seat.

"Ten minutes, then," she says. "And I don't know what you've been told, but I can't speak to the dead - thank God. The dead are quiet. That's why I chose to work in a mortuary."

"I don't want a medium."

Molly glances at him and then briefly at a point to his left and then back again.

"I can't tell you what happens after you die either. I don't know much more than you do and what I do know probably isn't what you want to hear."

"I don't care about that either," says Sherlock.

Molly looks at him curiously. "Then what do you want?"

"An explanation," Sherlock says. "You can't speak to the dead but you do see things other people can't, don't you? Things most people wouldn't believe in?"

"Maybe," Molly says cautiously. "Why do you want to know?"

"When I was six years old, I fell out of a tree…." Sherlock tells Molly the story of his visits from the grey stranger. She listens quietly and without comment, eyes fixed on the table in front of her and face kept carefully blank.

"So, you want to know how to make these – visions – go away?" Molly asks at last, once he is finished.

Sherlock blinks at her. "Of course not. I want to find out where he is and what he is. I want to talk to him."

"Oh," says Molly, and her hand shifts to cover her mouth a little too late to hide the smile pulling at it.

"Is something amusing?"

"Oh – no, not really. It's just –"

She stops, eyes wide, clearly caught with indecision about whether to tell him something. Sherlock swallows his irritation and gives her a reassuring smile.

"Go on."

"Well - I can help you with the first one. He's sitting right next to you," she inclines her head to the left of Sherlock.

Sherlock jerks around sharply to stare at the empty space beside him. There is nothing there.

"I can't see anything."

Molly sighs and picks up her teacup, taking a careful sip. "No," she says. "You wouldn't."

Sherlock rounds on her. "Explain."

Molly's eyes fix on the cup. "You know, there are some things most people are happier not knowing."

"I'm not most people," Sherlock snaps. "I need to know. Why is he here?"

"He's here because you're here." Molly says.

Sherlock grits his teeth at the non-answer. "So," he says. "I'm being – haunted?"

"Not any more than everyone is." Molly says. Her thumbnail taps against the mug for a moment before she clearly makes a decision, opening her mouth to and saying. "He's your Death."

Sherlock stares at her. "My what?"

"Everyone has a Death. It's just that usually they can't see them. Your Death is born at the same time as you, and they grow up beside you. They watch you every day of your life, and they – wait. Until it's time. Then they.."

"Murder you?" Sherlock asks.

Molly giggles. "No! Well, not really. I don't think they actually kill you they just sort of – guide you into, well. Whatever comes next."

Sherlock frowns. He thinks of the grey boy under the tree standing with eyes wide and his arms outstretched. The man lying on the carpet beside him, directing Sherlock to the phone.

"He didn't seem like he wanted me to die," Sherlock says. "He was telling me to keep trying."

"Yes, well," Molly picks up the plastic wrapped biscuit by the side of her mug and rips it open. "Being Death is a job. It doesn't mean they have to like it." She takes a bite.

Sherlock turns again to frown into the empty space beside him. It looks completely ordinary, completely lacking in any indication that there is any kind of supernatural presence occupying it. He reaches out a hand into the space but all he finds is empty air.

"His name isn't James," Molly says.

"What?" Sherlock turns around to look at her.

"He told me to tell you. He hates it when you call him that. He's called John."

Sherlock breathes out. It confirms more than anything that Molly isn't lying to him – the only person who could possibly have guessed about Sherlock's name for the grey boy was Mycroft and even he was unlikely to have deduced the real reason for Sherlock's Treasure Island preoccupation.

"John," he repeats to himself. It has a comforting ring, causing a reverberation deep in his chest. Yes, he thinks, that's right. He considers for a moment.

"Does John want to say anything else to me?"

Molly turns to look at the empty space again, then leans forward inclining her head as if trying to listen to something very faint. Then she leans back and looks at Sherlock, an oddly thoughtful expression on her face.

"He says he thinks you're brilliant," Molly says. "He says he doesn't think people tell you that often enough."

Sherlock stares at the empty space, suddenly at rather a loss for words.

"He also thinks you're an idiot, and that people don't tell you that often enough either," she adds.

Sherlock finds himself actually smiling a little despite himself. "He's not that observant then."

Molly frowns, craning forward across the table again, then turns to look at him, her dark eyes troubled. "He says you should stop thinking about him – that it isn't your time yet. You should be focus on looking after yourself and on – on your work." She gives Sherlock a curious look. "You didn't tell me you were a detective."

"Consulting detective," Sherlock says. "Only one of my kind." He looks back to the space beside him. "Is there anything else?"

Molly shifts, kneeling up on her chair to get closer to the empty space.

"I'm sorry," she says. "Deaths are always quiet – it takes a lot of effort to listen to someone else's. I think that's all I can get for now."

They both fall silent for a moment. Sherlock angles his head towards the space where John supposedly is, trying to sense – anything. God, he thinks, this is frustrating.

"Are you OK?" asks Molly.

Sherlock shakes himself inwardly. He is here to get information, he reminds himself. It would be foolish to let an opportunity like Molly Hooper go by without making the most of it.

"You say everyone has a Death?" he asks.

"Yes. Mine is standing by the door. His name's Toby," Molly gives a little wave across the café. "He can't come any closer because-" she stops short, face suddenly flooding with colour.

"Because?"

Molly's mouth twists a little, reluctantly. "I'm going to have a long life," she says. "The closer your Death is to you…."

"The closer you are to dying." Sherlock says. "I understand." He pauses. "You told me John is sitting beside me."

"Yes," Molly gives him a wide eyed look of sympathy that Sherlock finds instantly irritating. "It's odd though," she adds. "I've never seen a Death behave the way yours does. Usually the death stays at a stable distance, they move closer by inches, over years. But yesterday, he was half a corridor away from you. If you'd asked me then I'd have guessed you'd live to be ninety. Otherwise I wouldn't have... well."

"Yes, quite. No point in dating a dying man." Sherlock agrees.

Molly bites her lip. "I didn't mean…"

"You did." Sherlock says. "No matter – it's irrelevant." Sherlock picks up his cooling coffee and takes a sip from it thoughtfully. "What would make a Death behave so uncharacteristically then?"

Molly shrugs. "I'm sorry – I've no idea."

Sherlock eyes her thoughtfully. "Deaths aren't all you can see, are they?"

Molly shivers slightly and pulls her mug closer to her. "No. There are other things that aren't nearly so pleasant. Nor so quiet."

"Such as?"

"Believe me when I say, you really are better off not knowing," Molly says. "It frightened the life out of me at first. I nearly ended up in a psychiatric ward."

"You weren't born like with this ability then?"

"I had childhood epilepsy," Molly says. "One day I had a fit and it just seemed to knock something loose. My mum thought it was a gift from god – hence the whole Mystic Mary thing. She thought I could make my fame and fortune giving people spiritual comfort but it didn't work that way. The things I could tell people mostly weren't what they wanted to hear."

"You have a lot of dissatisfied customers on the web," Sherlock says. "It was what clued me into the fact you might have a genuine talent. A charlatan would have told people comforting tales about their dear old Granny being surrounded by angels and shining lights. You told people the truth."

"Much good it did them," Molly says. "They always finished up looking like you do now."

"Oh? How do I look?"

"Frustrated. Sad." Molly says. Sherlock opens his mouth to contradict her, but finds he cannot. A bleeping noise goes off and Molly checks her phone.

"Sorry," she says. "I have to go. Work calls. I hope this – you know – helped."

"It did," Sherlock reaches out a hand to take hers, and gives her as sincere a look as he can manage. "Thank you, Molly Hooper."

Molly gives him a lopsided smile and gets to her feet and, with a swift nod at the empty space beside him, she leaves. Sherlock sits for a while in the empty booth sipping his cold coffee. Eventually he gets to his feet and looks at the empty seat.

"Well then," he says. "I suppose it's just you and me."

Sherlock had never been quite so aware of the emptiness of the space around him before, the unforgivingly blank quality to the silence that greets him when he makes an observation, or a deduction. Knowing that John is there and that Sherlock can't see him is a constant nagging irritant.

After a month of frustration he buys himself a skull and places it on his mantelpiece where sits as a grinning reminder of the presence that eludes him. It doesn't help.

It must theoretically be possible, Sherlock thinks, to recreate an event in the brain like the one that had caused Molly to start to seeing Deaths. He does some digging and manages to find Molly's old MRIs – those after her epileptic incident show increased electric activity in the right parahippocampal gyrus. Any method of causing the same aberration in his own brain that Sherlock can research seems worryingly imprecise however – he does not wish to damage his intellect, certainly not without any assurance that it would actually work.

The problem seems impossible to solve, and Sherlock returns to taking cases again simply to distract himself from it. As it turns out this was the best possible thing he could have done.

The case is an intriguing one. Three siblings by the name of Tregennis living in an old house in Hampstead had apparently been sitting playing cards late into the night. The cleaning woman came round the next day to find the sister sitting stone dead in her chair and the two brothers gibbering wrecks. Lestrade texts Sherlock immediately and he arrives before the ambulance to find two brothers frothing at the mouth and writhing in their chairs.

"They've gone completely doo-lally," Donovan remarks to him as he enters. "Can't get a word of sense out of either of them."

Sherlock nods and, ignoring the corpse and the afflicted brothers, begins a survey of the room. No signs of a break in, very little out of the ordinary at all, except – Sherlock bends down to take a closer look – there is a peculiar fine residue in the fireplace.

"Your grey man is getting closer," a voice says from behind him.

Sherlock spins around.

"What?"

One of the brothers has got to his feet and is shuffling toward him, staring at him with a demented grin. "Your little grey man! Every time you look at that he gets a step closer." The man's eyes bulge as he points at the fireplace. "Like grandmother's footsteps, innit? Step, step, step…Arrrgh!" The man lets out a shriek so blood curdling that Donovan starts and turns around to glare at them both.

Sherlock looks back down at the fireplace, and then at the space behind him. "Interesting," he says. Carefully he sweeps a sample of the powder into a bag and pockets it.

A little research makes the cause of the Tregennis family's distress apparent: radix pedis diabolis a rare and dangerous compound made from a plant derived from the Amazon rainforest – apparently Brenda Tregennis' boyfriend was a naturalist who has brought the substance back for research purposes, and it had been stolen and used to devastating effect by a fourth, more murderously inclined sibling. Having solved the case, Sherlock leaves it to Lestrade to make the appropriate arrests, but fails to mention the small bag of evidence still sitting in his trouser pocket.

A trip to the anthropology section of the British Library and Sherlock is furnished with a rather intriguing set of insights into the terrifying drug. Apparently it was historically used in Amazonian tribes as a rite of passage for those who wished to become Shaman. One in three of those who consumed the drug died as a result of it. Many of those who survived lost their wits as a result. Of those who survived with mind intact, however, it was said that their eyes were opened to a world beyond imagining.

Sherlock turns the bag over in his fingers and thinks: it's a chance worth taking.

Sherlock sets his experiment up carefully. He arranges himself near an open window in his flat, places the powder on a small plate with matches beside it. Then he takes his phone and composes a text to his brother.

Conducting potentially lethal experiment (radix pedis diabolis). Tell your lackeys to wipe their feet before they enter, the carpet is new. SH.

Sherlock strikes the match and sends the text at the same instant. The powder fizzes slightly under the flame, emitting a thin wisp of smoke. Sherlock leans forward impatiently, inhaling, but nothing happens. He stirs the powder and strikes a second match. This time the powder ignites with a crackle, yellowish flame creeping across the plate. Sherlock breathes in….

And screams. The terror is instantaneous and wrenching. Every shadow in the room seems to have leapt to life and to be leering at him with a menace Sherlock has never encountered in the most determined of killers. His heart clenches painfully in his chest, and Sherlock finds himself desperately trying to draw in a breath but smoke is rising from the powder in thick choking billows. He scrabbles for the window attempting to open it further, when a face swims out of the eddying smoke, pale grey and hardened with anger.

"What have you done?"

Sherlock takes a deep gasp of the freezing night air and finds himself falling backwards into the dark.