"Are you really that surprised?" Sherlock sighed at John when he returned to 221B.

"It's downright immoral," the doctor growled as he paced around the flat. "They took an oath!"

"And you've sworn to kill me innumerable time yet you never had any intention of doing so."

"These are people's lives at stake, Sherlock! People trust their doctors and whichever evil son of a bitch is doing this…" John paused. "I know them, don't I?" Sherlock looked away. "One of my colleagues. It's one of my… Oh my god."

Knees shaking with shock and anger, John sank back down onto the sofa facing the coffee table where the contents of Kitty's file had been laid out. Sherlock watched him patiently, but a slight flicker of annoyance itched at the back of his mind. John had been reading that file for the entire remainder of the morning, how could he be so stupid? Unable to bear more than fifty-three seconds of dead silence on John's part, the detective took a breath to speak, but before the first syllable could escape, John's brain finally became functional.

"The doctors who performed the surgery – their names are in here, aren't they?" Sherlock's eye roll was so dramatic that John actually scowled in response whilst he flicked through the pages to find the list.

"Here."

John passed the report over to Sherlock, who immediately branded their names into his memory palace. Lewis Marshall, Paula Diggory, Georgina Thomas… "Matthew McNaughton. Who's that?"

John brightened slightly at the mention of this name. "Oh he's brilliant. Specialises in open surgery, particularly coronary. Did a transplant last year, some thirteen year-old kid. Saved his life. Sometimes he comes in to work on my ward. Good looking fellow, too…" Sherlock shot him a sharp glance. "What?"

"Nothing." Sherlock was trying very hard not to appear annoyed.

John chuckled in disbelief. "Alright, so maybe I had a thing for him." Sherlock's eyes shot daggers. "I never did anything. I was with Mary. And you were away so you can stop acting so jealous."

"He might just be our killer." Sherlock felt good about that.

John shook his head violently. "Nope. Not him."

"He was primary surgeon during Kitty's operation. He put the stent in himself. We have to at least consider it," Sherlock pushed.

"He's a good man, Sherlock. It's not him. You can look at me like that all you want, it won't change my mind. You can tell what sort of person someone is just by looking at them, and I may not be so clever, but I know Matt's no killer."

The detective could hardly understand John's fixedness. He gazed at his Watson, so assured and confident. Sherlock knew that it was just a matter of trusting him, and there was no one in the world he trusted more than John Watson.

"Alright," he conceded quietly. "Not McNaughton. What about the others? Previous incidents where people have died? Has Kitty had recurring treatment from one of them?"

Satisfied, John pulled out a few more sheets. "Kitty used to go see Dr Selmy once a month to get her prescription updated. She's had a, um, psychiatrist since you jumped off the roof. Can't blame her to be honest, she must've felt awful… Sorry. But she would've felt guilty as Hell for publishing all those stories about you… Yeah, okay I'll shut up now."

There was something lodged in Sherlock's throat when he tried to speak again. Perhaps it was guilt, or shame. The sting of responsibility bit deeply into his heart, regardless of every effort he made to prevent it. Kitty deserved it, he told himself. She deserved to be hurt. His stomach lurched even as he thought it. He couldn't blame her for doing her job in an attempt to win her stripes. He couldn't blame her for believing a credible lie; a lie he'd encouraged. John, Mrs Hudson, Lestrade, Kitty… Who else had been and would be affected by his fall? It was selfish to have done any of it, but all he'd ever wanted was John, safe and alive and well. But at the cost of people's happiness, people's lives? He'd broken his own vow a million times over. All the people he'd killed. When he'd told John, he'd passed it off as easy and remorseless because they were all evil people. Sherlock knew better. Some of them had had families, families who missed them. Young children, husbands, wives, mothers, fathers… All of them Sherlock's victims. All for John. The scale was sickening. But he would never tell his husband. When he glanced back at John's kind eyes which had just so recently flashed with admiration, joy and love, he could no more tell him than he could leave him again. Sherlock wondered whether those two things were now synonymous.

"We'll need to go see the psychiatrist," Sherlock confirmed, shoving his reminiscing out of the way of his work. "And I'll need to visit everyone on the list."

"We can go tomorrow. I need to get back to work, Sherlock, please," John begged after a look of disapproval was sent his way. "It'll be easy for me to observe them there. We can catch this murderer quicker than if I stayed at home."

"The same murderer might just as well kill you."

"Moran wants to kill me himself, you know that," John reminded him. "I'll be safe. Your brother's bodyguards can look after me."

Reluctant as he was, Sherlock had to agree. It would be quicker to find the murderer if John was to be his eyes and ears in the hospital. Allowing John to work meant that Moran would constantly know John's whereabouts, and his doctor minion would be able to tell him what John was doing. But Sherlock's body count was high enough. He couldn't give this treacherous surgeon the opportunity to kill any more people.

"Fine. You'll have Mycroft's people on you at all times, and I expect you to text me to meet you when you're on your lunch break. Every day." John reached out to grab his husband's hand with gratitude, and Sherlock allowed him to take it. "I know when your breaks are so don't you dare forget to text me or I'll be straight there and storming around the entire hospital until I find you."

"I won't forget, I promise," John beamed. "Thank you, Sherlock."

"I'll phone Lestrade, you call my brother. They need to be aware."

John paused. "Is Molly in danger?"

"I hope not," Sherlock said, absolutely serious. "But if they're trying to get to me, Molly would be one way to do it. Look out for her, John."

"Of course I will," the doctor said, but the slight tremble in his voice said something else.

It said: I don't know whether it'll do any good. The detective couldn't keep his sadness out of his eyes as John stood and kissed him, and he couldn't keep a sense of dread from chilling his bones right down to their cores.