Their cab stopped in front of an abandoned bottling factory on the outskirts of London, standing black and ominous against the overcast morning sky. Assorted police officers were standing about, ignoring the doctor and detective as they strode in. Most of the regular officers had become so immune to their presence that there was not even a glance spared between them when the pair appeared; it had just become another facet of their daily lives, not worth the attention.

Inside the cavernous front room, bobbies scurried about, most staying clear of the circle of floodlights illuminating a small, thin figure lying prone on the ground, covered in blood. It was difficult to see outside of the ring of lights, their glare causing John to wince, but he could make out Lestrade in a corner, conversing intently with Sally Donovan. He breathed a sigh of relief. At least the officer wouldn't be calling his boyfriend a "freak" when her attention was captured by the Detective Inspector.

Anderson was waiting for them at the entrance, his lip curled angrily as Sherlock's tall, black figure strode toward him. "If you tamper with any evidence, I'm telling Lestrade to bar you from any future crime scenes."

"Ooh, telling Lestrade on me? What a potent threat, Anderson. I have plenty of things I could tell Lestrade as well."

"Like what?" The medical officer glared reprovingly at the detective, who merely brushed him aside.

"Two words, Anderson: squad car. One more: Sally's squad car. Need another?" Sherlock wore a frightening grin, his teeth gleaming ominously in the semi-darkness. Anderson blanched, falling silent.

John merely rolled his eyes, moving past both of them toward the body. "Children, stop bickering."

Sherlock immediately abandoned his squabble with the Yarder, his coat snapping briskly in the cold, drizzly wind of a London Sunday morning. Taking up stance beside John, he merely watched as his partner meticulously examined the body, but his eyes danced across the prone, naked figure, picking up thousands of clues with each twitch of his optic nerve. Pure, unfiltered data poured into his mind, neatly arranging itself chronologically, categorically, and by order of importance; his fingers were practically writhing, impatiently awaiting their chance to add to the flow of clues.

John drew himself up, stepping away from the body and crossing his arms, squinting.

"Well, John? What have you determined?"

"Victim was in his mid 30's, female-to-male transsexual, had undergone metoidioplasty as well as a bilateral mastectomy. Judging from the healing of the scars, the mastectomy had been about 15 years ago, while the metoidioplasty had been relatively recent – about five years. He was married judging by the ring on his finger; that means that either his partner is a female, his partner is male and he never had his gender marker legally changed – unlikely, from the length of treatment and the metoidioplasty – or his partner is male and they had a civil partnership, but chose to wear wedding rings. So no clues on that. Wallet and ID were gone or we would know more info already, according to Lestrade. They're going to run dental records."

"Good," Sherlock replied absently, already mulling over the info he'd determined.

". . . Should I go on?"

"Yes, yes, of course."

"Victim has been dead less than 24 hours. This was definitely a hate crime as you determined. The attacker has probably done this before judging by the surgical precision of the wounds and the fact that he went for the groin and chest first, then the killing blow. He wanted to incur as much pain as possible in the genital and the chest area. There are bruises on the victim's throat and upper chest, which shows that the attacker held him down while performing at least part of the damage. It was almost like he was attempting to undo the sex reassignment surgeries because he cut off the penis, then plunged his knife into the wound and twisted. As you can see he reopened the incisions from the mastectomy, took the victim's shirt and underwear and inserted them underneath the wound." John's voice began to lose its authoritative nature, and his skin was tinged a slight green. Sherlock noticed immediately, resting his hand on his partner's arm.

"You don't have to go on if it upsets you," he said softly.

"No, I –"

"What are we looking at here, Sherlock?" Lestrade's booming voice cut through their conversation, and the Detective Inspector strode up, a clipboard in his hand. "Ghastly, that," he offered, almost companionably, and the consulting detective nodded. John stepped back, his lips pursed, and looked away from the crime scene, fighting to push back the bile rising in his throat.

"John has been performing a physical examination of the body for me. This was a hate killing, a transphobic hate crime against the victim, but not him personally. The killer tracks his victims through the NHS, which suggests that he has a job in the healthcare system. Judging by the handspan of the bruises on the victim's throat, we are looking for a large, cisgendered man. I would put him at about 6'4", massive build and a very strong grip." Sherlock knelt down, running his gloved finger carefully along the pectoral cuts. "This was made with an autopsy blade: disposable 8" Sheffield disposable steel dissection knife, distributed by Mopec Europe; they have these at Bart's, I've used them before," he offered by way of explanation for his knowledge. Lestrade nodded.

"The fact that he used a disposable dissection knife again suggests that he works at a hospital or a forensics lab: he has access both to the knives – and these are not cheap – so that he could smuggle them out as well as access to the sharps bin so that he could throw away the knife without suspicion. There would be no questions about it, why would they be concerned? The wear on the blade would have been identical to that of an autopsy. The missing knife could be explained as he accidentally used one to saw through a bone, it snapped and he had to replace it. He may have even snapped another disposable knife to further add to the ruse. Forensic pathologists, especially those on call, often work irregular hours, which would mean there would be few witnesses when he returned to his place of work and, again, little suspicion aroused by his departure and return.

"The cuts are extremely clean and done with admirable precision. The blade, therefore, is quite sharp, brand new, and the man who wields it has at least 20 years of experience in performing autopsies. However, this is not his native knife, as shown by the hesitation at the onset of the lines. A man who has worked that long in forensics would have earned a preference for certain types of knives, gained a native intuition on to how to use them: he wouldn't have faltered in the beginning of a cut if this was his typical instrument. This suggests that he has a personal set of tools that he uses; perhaps he is a coroner with a sterilizing machine? At points there is a little scattering of the line and of the blood spatter. This is where the victim moved and disrupted the murderer's concentration – remember, he's used to working on inert bodies and the breathing and twitching of a live victim is erratic, difficult to account for. However, the way that the line quickly recovers shows that he has performed a similar murder to this before."

Lestrade nodded, deep in thought, while John reached for Sherlock's hand. "Brilliant. Just brilliant."

The consulting detective offered a wry grin. "I pride myself on my work."

"Understatement of the century," Lestrade rumbled. "So we're looking for a very experienced forensic pathologist or undertaker with a vendetta against transgendered people?"

"Yes, in short. But remember he has to have access to the NHS database in some way. This means that he either has friends who work directly with the system, or he works in a smaller hospital with less stringent security policies. He might work with the system himself. A vendetta like this generally is based in personal history or trauma. This is a dedicated serial killer – this man," Sherlock gestured to the corpse before them, "had been living as a man for at least ten years. The killer had to perform a meticulous search for him, making a highly illegal search for his personal information in the healthcare database and then tracking him down to his home."

At Lestrade's raised eyebrow at the last sentence, Sherlock sighed, irritated by the detective inspector's clear lack of understanding. "Yes, by the way, he was brought here. Look at the small stand of cloth caught between his teeth – he was gagged, but not bound. This leads me to conclude that he was drugged with a muscle relaxant in his home before being brought here. The gag was purely for psychological torture: even when people are cognizant of the fact that they can't speak, a gag reinforces this and causes more tension. It appears that the relaxant had worn off shortly before he performed the pectoral damage, but not before the genital torture."

"Good, Sherlock. Thanks. Is there anything else, or should we start looking for the killer?"

Sherlock almost replied, explaining that he thought he knew the identity of their target, but John interrupted him.

"I know something."

They both turned to look at him, but the doctor had his eyes solely on Sherlock, his jaw set.

"There is no way in Hell I am letting you go to Bart's, or any other hospital, before we find this psycho. Understood?"

"But, John-"

"Understood?"

Sherlock ran his eyes across John's face, as if examining his intent, and then he nodded softly. "Yes, John. Of course."