Sherlock did not say a word as they made their way out of Barts and down to the street to wait for a cab. The afternoon was freezing, and even Sherlock, always so desperate to pretend the sensory limitations of being human did not apply to him, was visibly shrugging himself into his coat, as if he could disappear into it. Obviously not a good time for idle chit-chat. It was only when they were in the cab and well on their way back to Baker Street that Sherlock finally asked, "Why wasn't it kinder?"
John scrambled his thoughts together. What wasn't kinder? Oh. That performance he'd put on back at the lab. Poor Molly. Nothing ever went right for her. "Are you seriously asking me why what you just did to Molly wasn't okay?"
"No, I'm asking you why it wasn't kinder." Nobody, John thought, made a better job of haughtiness than Sherlock—unless it was Mycroft. Since he knew better than to interject, Sherlock went on, "Molly's new boyfriend is fundamentally uninterested in her. His appearance, his personal grooming, and most importantly, the fact that he left me his phone number indicates he's well aware of his own preferences, which rules out self-delusion as a motive for a relationship her."
"Maybe he's bi."
Sherlock apparently did not hear this remark. "Now, for example," he went on, "if a man is in a relationship with a woman for six months, only to find out she's not even sexually attracted to men, let alone him specifically, and was just using him as a way of gaining access to the woman she was genuinely attracted to, how would it be a kindness to him to not tell him as soon as possible?"
John cleared his throat, one fist to his mouth, trying to keep a grip on his temper. He doesn't know any better. And an innocent woman had six hours to live unless Sherlock was able to solve the mystery behind the trainers left in 221C. This was hardly the time to get into an argument with him about what was, after all, over and done with. "Let's get one thing straight," he said finally. "We don't talk about Clara, right? Ever."
Sherlock opened his mouth to make some smart remark, then, seeing John's expression, shut it again, gazing out the window in obedient silence.
Does he even know any better? Almost three months of being flatmates, and John hadn't yet decided how much of Sherlock's rudeness was deliberate cruelty and how much was a kind of childlike literalness. While he was impervious to most attempts to get him to behave like a human being, occasionally he overreacted to being corrected, and then John felt like he'd slapped a toddler for touching a pretty toy or chasing after a puppy.
Finally, after the silence had become too uncomfortable to bear, John said, "Can we talk about the case now? You kind of forgot to tell me who Carl Powers is."
Sherlock was still looking out the window and appeared not to hear the question. Just as John was on the verge of reminding him that there was a terrified hostage who needed him to stop being so bloody childish, he snapped out of his reverie and said, "1989. A young kid, champion swimmer, came up from Brighton for a school sports tournament, drowned in the pool…"