Sherlock has concluded that Presbury has consented to whatever the Clinic is doing, and that he is aware that whatever it is, it is not something strictly legal. He knows why Mycroft wants him to dig at this, too – not enough proof yet for official channels, and a degree of deniability. With this in mind, he makes arrangements.

(A passcard, a generic uniform given a few tweaks, a backdoor wifi connection through a receptionist's terminal.)

So John comes blearily downstairs one morning to find a strange young man uploading the contents of a flashdrive onto his laptop.

Merc is a lean, pallid creature, slightly better dressed than a lot of Sherlock's contacts, but still with that edgy, feral quality John associates with some kind of addiction. In this case, it is the marginally more socially acceptable kind, technology. John doesn't know how he hacked into the Clinic, doesn't want to, knows he wouldn't understand if he was told. But the laptop is now stuffed with incriminating and illegally obtained files.

He's still expostulating about that, and the fact that Merc has had the last of the milk in some industrial-strength coffee before he slunk out, but Sherlock has tuned that out, busily raking through the data.

However deferential and ego-stroking the experience may be, the Camford Clinic is still essentially a business. The financial records and membership lists are prosaic. The Director, Anton Dorak, might not be a doctor, but he obviously has some very shrewd insights into human nature. Make something seem secret, exclusive, and people will clamour for the privilege. The very highest level of all is 'White Card'. How droll. Sherlock filters those names. John runs his eye down the list, makes a soundless whistle.

"Bloody hell, Sherlock, this is a tabloid journalist's wet dream..."

A couple of the names are very familiar, and he's fairly sure that he's seen others go by in screen credits. At least one is the real name of a pop star.

"No athletes, though." Sherlock muses.

"Drugs tests." John says, still reading. Looks up abruptly. "It's something that leaves a trace in the system. You may be right about the injections."

Sherlock ignores the 'maybe', disdainful. Of course he's right.

"Erratic behaviour in those of a bohemian profession is almost expected. They didn't notice the side effects until they started dosing someone normal...Ah, this looks promising."

Sherlock's knowledge of biochemistry as it relates to poisons is unparalleled, but he is neither a scientist, nor a doctor. However, he has a doctor to hand, one who is reading over the notes with a certain degree of sick horror in his face.

"These letters are from... my God, Doctor Laszlo Lowenstein."

John is no expert, but he keeps up to date with certain medical journals, and the name is familiar. A couple of years back, there had been a small uproar about some revolutionary, and unfortunately highly unethical, work with gene therapy.

It seems that Lowenstein has continued his work, unapproved by any official body, taking his funding from what amounts to his test subjects.

John tries to wrap his mind around the idea of people so desperate to hold onto or regain their youth, that they will allow themselves to be used in this procedure. Of scientists who are so intent on playing at God, that they regard humanity as something to be taken apart, reconstituted, spliced together in a laboratory. He's not a religious man, but the idea of something simply created to be just human enough makes him queasy.

Sherlock regards the idea with curiosity. How much of the effect was psychological? Increased strength and agility, with no apparent loss of cognitive faculty... But John is still raging about the perversion of scientific research. Sherlock interrupts.

"Without experimentation, there would be no progress."

"There's a world of difference between trying to cure senile dementia, and just allowing rich idiots to act like they are twenty again..."

"Yes." Sherlock interjects, faint malice. "Vanity is more profitable."

"...This isn't proven medicine, this is screwing around with nature without constraint." Runs a hand through his hair, and the tremor is not feigned. "Christ, who knows what this stuff will do to these people in a couple of years time?"

Xenosis, the possibility of cross-species infection. HIV, CJD, a whole alphabet soup of things that could break free and riot through the body.

John abruptly remembers that he's talking to a man who has injected himself with things quite as harmful, if better known. Sherlock lifts a shoulder, doesn't quite look at him. John glares.

"No, you don't get any of it to play with." He growls. "Do you really want to start swinging around London, pretending you're Tarzan?...no, don't answer that. You are not shooting up genetically modified monkey hormones, and that's final."

00000000

Lestrade, fresh from the raid upon the Camford Clinic (an anonymous tip-off about possible animal rights activists, and a bomb threat, has uncovered some surprising things,) is sure that something else is up, but the arrival of a sleek black car that disgorges a sleek Mycroft Holmes also makes him sure that he won't find out what. A pretty woman with a Blackberry spares him a sympathetic smile as he is borne away from the scene. He's not terribly surprised to find Sherlock lounging sulkily in the car, or that his ever-present shadow is giving him a strained smile.

Presbury blusters, blanches, collapses back into his chair, when the tired-faced DI explains to him that he has been implicated in a biotechnology scandal, and that he should probably seek both legal counsel and further medical opinion. The quietly official man says little, but his presence seems to withdraw warmth from the room. This is an ignominious end to a career. Possibly to a life.

Sherlock himself is supremely uninterested in the aftermath, now the puzzle is solved. How Mycroft wants to spin this, cover it up, expose it, makes no difference to him. But John, honest John, wants to break the news to Edie, feels a personal responsibility. Drags Sherlock with him.

The problem is that Edie Presbury promptly surges forcefully back down the corridor, her usual entourage of dog and boyfriend now supplemented by a heavyset blank-faced man who simply screams 'security detail'. But even MacPhail can't stop the daughter of the house from blasting into her father's study and yelling at him.

"Dad, I'm not letting you keep injecting yourself with that junk just because you want to impress that bimbo!"

Presbury starts up out of his chair, face distorted with temper, arms raised. And Roy surges forward, slipping his leash to defend his mistress. Both Edie and Presbury shriek as the teeth close, and man and dog go down, a growling, screaming, thrashing mayhem.

It is a seemingly quiet and unassuming man, who surges forward, barking orders in the tone of voice which expects to be obeyed.

John Watson has seen worse injuries than these, worked under gunfire. But it doesn't matter that he is kneeling on clean carpet in the suburban calm of England, and not in the sunbaked dirt of a foreign warzone – as a doctor, his enemy is always the same.

Bennett has his hand twisted tight into Roy's collar, hauling the animal back. It is left to Sherlock to restrain a shrieking Edie from flinging herself into the situation.

00000000

Presbury looks his age, now. Grey and crumpled, all that borrowed vitality drained away. Edie, white and worried, is holding his undamaged hand. Bennett is pulling a reluctant Roy away from the ambulance.

"The courts will probably want to have that dog destroyed." Lestrade says unhappily.

"I don't think so." Mycroft's measured tones beside him. "After all, the animal's perception is what uncovered this whole scheme."

"People are so ridiculously sentimental about their pets." Sherlock mutters.

"Yes." Mycroft moves his calm gaze from his for-once oblivious brother, to the object of Sherlock's attention, a slightly worn figure in a battered jacket who has been checking the neck dressing, handing over care to the ambulance team. John looks exhausted, unconsciously working his own shoulder. The talk of physio has caused a reminiscent ache. Sherlock steps beside him with a brisk swirl of coat.

"We shall be in the local pub if you need us. Come along, John."

Sitting down somewhere warm sounds rather good to John. He's already moving towards the door, his slightly uneven gait matched to the long impatient stride.

"His master's voice." Lestrade murmurs, before he thinks. Cringes faintly. But Mycroft gives him a thin, not unfriendly smile.

"Indeed. But there are worse things in the world than a faithful watchdog, Inspector. You and I know how far off the straight road my brother could tread if he didn't have someone to guard him from himself."

Sherlock forgets to eat, dismisses the need for sleep, is reckless with his own health and safety. But he's prepared to drink (or at least sneer at) warm beer in a tacky pub, and watch while John works his way through pie and chips. It's a start.

00000000

a/n – Clearly, I'm a writer, not a scientist. Hence the deliberate vagueness on some points. This is treading on the toes of sci-fi, not fact. But I didn't have to do very much to the central premise of the original story. People have always tried to desperately hold onto or recapture youth. When Conan Doyle wrote 'The Creeping Man' in 1923, a surgeon named Voronoff was experimenting with the transplantation of monkey glands into humans as a longevity treatment. This was still the stuff of nightmares to many people, shades of H.G Wells' Dr Moreau. Now, HRT is common place, and heart valves from pigs are routinely used in surgery. But the fear is still there, in GM crops, 'Frankenstein food'. A world of fish genes in your tomatoes, and monkeys that glow in the dark...

For a seriously creepy take on this subject, the artwork of Patricia Piccinini will give you nightmares.