In the muted twilight interior of the cab, as the sun sank sharply over the jagged horizon of London's skyline, Sherlock did what he did best – gloated.

This case may well have been his best: an estimated 20 murder victims would be revenged with one Harnot (nickname Hank) Andrew Farwether's arrest, Sherlock determined from the police reports he easily purloined from the database of the LGBT police liaisons. And John H Watson – his John H Watson – had been the linchpin that brought down the forensic pathologist (43, graduated from St. Mary's forensic pathology department class of 1989, worked for a small Shropshire undertaker before returning to the hospital at age 34, remained ever since). John, the protector, inadvertently shielding any further trans men from coming to harm: the thought spurred a tingle of pleasure down his spine. His John, saving lives without even knowing it.

Every serial killer made a mistake, especially when they targeted their victims out of a personal vendetta. Their blind rage blinkered them to anything but their goal of clearing the world of their hated subgroup: in this case, it had spurred Hank to attack an innocent man accompanying his transgendered partner to a pelvic exam appointment in a sleepy corner of central London. And oh, how unfortunate Hank was that the man he battered happened to be the ex-Army doctor, soldier, blogger, and lover of Sherlock Holmes. How exceptionally unfortunate.

His scuffle with John had put him on Sherlock's radar. He remembered him well – heavyset, about 6'4", strong calloused hands with pronounced veins through the arm and down to the thumb, suggesting that he spent a great deal of time working with his hands and enacting heavy pressure with the butt of his thumb. The bruises around John's neck and throat after the fight told Sherlock that Hank was likely to attempt to smother or strangle his victims to subdue them; when this very same pattern of abuse appeared on a trans man, after the violent outburst related to Sherlock's own transgendered status – well. It was easy enough to put the pieces together. Child's play.

Of course he had to test his hypothesis, gather data, but John, oh John. He was the mistake. He was the key to the whole puzzle, because without John's accurate description of his attacker's methods, Sherlock wouldn't have known a damn thing. How very fortunate they were that John had bullied Sherlock to the clinic on that very same day, and that the detective had dared to purr naughty things in his lover's ear! Sherlock reminded himself to always sexually frustrate John in public from hence forward: it clearly afforded them positive results in regards to potential queer-phobic serial killers.

But how to draw him out? How could he lead him along in a merry dance to his location, without getting his clitoris chopped off in the process? At the thought of genital mutilation to himself, he winced on John's behalf. The soldier did so love to 'go down' on him. It would be a pity to deprive him of that eternal pleasure just for something as trivial as a case.

Sherlock stopped himself, rewound the thought, and winced again. When did I make my work my mistress instead of my wife? No matter. She can't keep me warm at night. And she doesn't bring me breakfast in bed when I make that look John describes as 'sultry'.

Lestrade texted him just then, startling him out of his reverie.

victim's name Edward Jakes metoidioplasty April 5 2006.

Sherlock nodded. Not important at the moment. He returned to his calculation when his phone buzzed again.

anyone who got a metoidioplasty at 27 Devonshire Place Mews five yrs ago targeted.

27 Devonshire Place Mews shared the same subway stop as Baker Street; it would make sense for him to have gone there, had he chosen to have a metoidioplasty. Of course, he hadn't been living at 221B Baker Street five years ago, but his friendly serial killer wouldn't know such a thing. His phone buzzed once more.

seven trans men on the missing persons list who had their surgeries there 7-5 yrs ago.

Sherlock smiled triumphantly. A solution offered to him that was beyond beautiful – elegant really.

The serial killer would strike again soon, he knew it. He would make this personal, draw him out, draw him here, and it would take little more than –

He huffed. Mycroft. Of course. That incessant bloated gnat would have to be involved. Sherlock had plenty of advantages to the average serial killer, but complete and unquestioned access to every document in the government's databases was not one of them.

Need you to manipulate medical files. SH

Insert Sherlock Holmes, metoidioplasty, into medical files of 27 Devonshire Place Mews as of April 7 2006. SH

Do not insert address simply place [redacted]. Employer St. Bartholomews Hospital as transgender health researcher, mumble jumble something or other. SH

That would draw him out without question. A trans man with a metoidioplasty and an interest in advancing transgender health? Surely he would be a more satisfying kill than the average everyday bloke, with a record like that.

Sherlock thought deeply about the next step. John had neglected to press charges against Hank – his merciful nature was quite grating at times, really – but surely Hank would remember the name of the man who could have locked him up for good. As much as he would rather not place John in any matter of harm, it was the final treat to dangle in front of the murderer's nose. The most personal catalyst, designed to get under the transphobe's skin more than any other – killing the spouse of the man who had bested him in a fistfight. What could be better to soothe the psychic wounds of a deranged man?

Place Dr. John H Watson as spouse of Sherlock Holmes at time of metoidioplasty. SH

He smiled a little. Hopefully his future medical records would bear that information genuinely.

The cab jutted to a stop, and Sherlock glanced up at the illuminated exterior of St. Bartholomew's Hospital, its angles grotesque in the newly fallen night.

He was placing himself into an unacceptable level of danger as judged by his partner. He was also breaking a simple rule that John had put into place to protect him. In fact, he was gleefully dangling himself in front of a deranged psychopath, instructing his brother to create false medical files in order to inflame the man's hatred for his kind, taunting a murderer into taking him on.

And damn, did that feel good.

Stepping into the cold, antiseptic air of the hospital, Sherlock strode purposefully to the stairs, taking them two at a time down to the pathology department. He could feel the vial of blood in his pocket sloshing about, reminding him to keep up the ruse of needing blood samples. Molly was, blessedly, working the night shift tonight: he'd memorized her schedule, knowing that her pathetic and unrequited crush on him afforded him a valuable minion whenever he required lab work that was deeply beneath him to perform.

He felt a quick twinge in his left leg, a psychosomatic sympathy pain he developed shortly after meeting John. It only hurt him when he was actively hurting his partner – a stopcock for his sociopathic tendencies before they damaged the man he loved. And he was doing quite a bit of damage tonight, to be sure.

There was a chance that he would not make it out of this encounter alive (66.8%, accounting for 40 different variables). That was an unacceptable danger in the eyes of his lover, who fretted if Sherlock left the apartment without a warm coat ("Pneumonia, Sherlock – I've seen far too many cases of coatless-induced pneumonia to be comfortable with your lack of a jacket") or stubbed his toe on a pesky stair step ("It could get infected! You could get gangrene! And necropsy! And die!"). He had learned to sacrifice in the name of criminology, to martyr himself for science's sake, but John – his sweet, lovable, fair-minded, caring, deeply empathic opposite in all matters of love and justice – would not, would never accept such a fate for the man he adored.

Sherlock bit his lip as the pain got worse, as if he had been shot in the leg. Sometimes he wondered if it was the only way he knew to show his affection: by hurting himself for his sake.

If I die tell John I would have divorced my work in a heartbeat for him had he ever asked. SH

Molly looked up as Sherlock shoved the doors open. "You're here late!" she commented enthusiastically, raking her eyes over his disheveled figure.

A little kindness wouldn't kill him, he decided. "And you're looking quite nice today. The aqua of your blouse brings out your eyes very well. Cool tones suit you, Molly."

The short lab tech nearly broke several capillaries in her face with the force of her blush. She smiled radiantly, practically vibrating with glee.

"I need a lab report on this vial of blood," Sherlock intoned, bringing the conversation back to the nature of his visit.

"Of course! Anything! Toxicology?"

"Yes, please. Also, if you can manage to tease it out, measure the androgen and testosterone levels as well as cortisol."

"Sure thing, Sherlock!" Molly chirped, bounding out of the room with the enthusiasm of a five year old on Christmas morning.

Sherlock smirked. Then his grin faded as he thought, once again, of his partner, sitting uncomfortably in Mycroft's office, probably fighting not to be pulled into his brother's gravitational field. He pulled out his phone, crafting a text, then put it away, steepling his fingers.

If his estimations were right – and they always were – he had about thirty minutes until the killer arrived. He had waited nearly a day, and would probably now be checking the NHS list again, finding a suitable recipient for his murderous hatred. He could use this downtime to untangle the gnarled threads of this mystery.

Why 27 Devonshire Place Mews? They were one of the only FTM surgery providers in London, but there were others in the surrounding areas. This suggested that, again, it was a personal vendetta. Someone he loved – or hated – had been treated at the clinic. They were transgender. Since he was killing only those with metoidioplasties, the object of his anger had been a trans man: not necessarily with that same procedure.

Metoidioplasties were merely the only surgery performed only on trans men, as far as Sherlock was aware. Hysterectomies common in post partum women. Mastectomies usually undergone by breast cancer survivors. Hormone replacement therapies affected both trans men and trans women – not specific enough. Phalloplasties sometimes performed on cisgendered men who had suffered severe penile trauma. It wasn't the actual surgery the man was interested in. It was a convenient and relatively easy way to find trans men without accidentally targeting another surgery recipient.

Strength and duration of the hatred suggested that the actual object of anger was long-dead, forcing him to take out his frustrations on those with similar backgrounds. Childhood trauma. Venting his anger and devastation at a transgendered family member by killing other trans men.

Brother? Unlikely – close enough access that killer could have simply done off with brother. Mother undergoing transition? Improbable. Ah!

Mother abandoned family, ran off with trans man. Father dead or out of picture. Trans man killed mother possibly? Anger of abandonment not enough – would have also targeted spouses of trans men as well, wouldn't have let John get away before killing him. John did not suggest he was in mortal danger and was able to subdue him without grievous bodily harm. Trans man ran off with mother , killed her. Most likely conclusion.

Sherlock sat back, a satisfied smile resting easily upon his lips. Base instincts led to elementary solutions for seemingly impossible problems. The human capacity for violence and transplanted hatred never surprised him.

Footsteps down the hallway: too heavy to be Molly's. Back-to-front toe motion suggested man in heavy workboots. Heavyset. Gait canted to right side; right-handed, heavyset man carrying a gun. Sherlock yawned. Gunshot wound – boring way to die.

"I guess I'm not good enough for the interesting death," the consulting detective groused, standing up and brushing off his suit. He reached quickly into his pocket and pressed the 'SEND' button on his phone, before the door slammed open and Sherlock stared his possible death right in the eyes.

Help. St. Barts. Hank. Run. SH