To John's credit, most of his medical training had been dealing with people while they were still alive -- hanging was rarely an instance that he had to deal with, and even fewer instances with rope. But now that it had been pointed out to him, he could see it plain as day and even went over the other photographs to confirm what Sherlock had told him. He was right. Absolutely, completely right as usual. Maybe that was what had been bothering him about it.

He's just about to open his mouth to produce a question as to why they would appear that way when Sherlock pulled him back by his neck. Immediately, his voice catches in his throat while he tries to figure out a) what the hell Sherlock is trying to illustrate, and b) whether or not this is even safe. If Sherlock wasn't expecting a struggle, well, there at least he would be wrong. He only felt his breathing restricted a little, thankfully, but that doesn't stop him from grabbing at the rope and pulling at it anyway.

Even if he knows that Sherlock means him no real harm, he can't help but feel that this could go very badly very quickly, and his chest tightens, his breath hitches, and his face... warms? It takes him a moment of tuning out Sherlock's lesson for John to realise that it's not just scary and dangerous, but it's exciting in its own way. He's not proud of the goosebumps he gets when the rope slides down his neck, either, and before his mind can wander any further, he yanks the rope away from his neck so he can duck under it to glare daggers up at Sherlock.

"What the hell was that about?!" he cries. He knows full well what it's about -- Sherlock so rarely thinks things like that through before he does them -- but John still thinks he's got right to be upset. "Have you finally gone.. completely insane? What the hell is wrong with you!?"