[He's looking off to one side, examining the servers, the other customers, deducing what he can. It's Sherlock's litmus test, what he turns to when he's feeling anxious, to make sure things are still okay.

By the time he's looked back at John, he knows everything he can about every one of them. All other faculties functional, which means it's time for an experiment.

He has to get John to tell him to do something. Something he would never normally do. Eating a bit more than usual isn't all that unusual. Changing his mind about the nicotine patch could have been coincidence.]

Still fine. But d'you know what I've noticed about those two over there. [He leans forward, indicating a couple that's sat a few tables down from them, and speaks in a low voice.] Her cat didn't run away. He had it put down. She suspects but doesn't want to say anything because she's so head-over-heels for him and they've been dating for at least a year, maybe two. Doesn't want to throw away the relationship over a suspicion. But she loved that cat. Constant companion. Possibly the hurt will fade over time, scab over, or then again it might fester, create an undercurrent of bitterness in the relationship. She may never fully trust him again until she knows, but she's afraid of the truth, which means subconsciously she does know and is only waiting for him to spontaneously confess, which is unlikely given that he clearly has at least two other girlfriends he hasn't told her about, or for a stranger to walk up and accuse him.

I'll just go and inform her, shall I?

[And when he stands up, he has every intention of doing exactly that.]