He'd recognized Jim the moment he'd walked into the morgue -of course he had, how could he not remember that face, that voice- but he hadn't wanted to say a word, not in front of John. Things had… changed since Uni and he wasn't going to be the first to relive that debacle.
So he'd allowed Jim to walk in and walk out, refusing to fully acknowledge the man's presence. Once he was officially out of the room Sherlock was able to look around and collect himself enough to tear apart Jim's costume while Molly's eyes welled up with tears and she stormed out. He could feel John's disapproval, but he didn't care.
It had driven him mad, hearing Jim's voice, having him right there, very nearly there but not entirely there, playing a part Jim, always playing, never truly there. Everything about the costume had been specifically done to torture Sherlock, to remind him of what once was. The clubber's eyes- at Uni it was Jim who would tug Sherlock away from experiments, laughing that mad laugh of his as he entreated Sherlock to "just come dancing with me, one night Sherly, please," and Sherlock would follow, laughing along with. The hair product- Jim had always had it around, despite the fact that he never used it, and Sherlock had teased him over it mercilessly. The pants- that was to add insult to injury. They'd belonged to Sherlock when they'd been together. He'd foolishly left them behind after a fight- the fight, and he'd never gone back to collect them or any of his other things.
Damn him. All this time, all these years, and when Sherlock most needed his mind present when he most needed to think, Jim had shown up, once again throwing Sherlock's mind into turmoil.
Not this time, Jim. Not this time, and never again.