Sherlock keeps trying to bug Mycroft about something, but Mycroft won't talk to him. So Sherlock drags John to the Diogenes Club and starts on a campaign of silent (but extremely expressive) PDA, in keeping with their new not-just-flatmates-anymore status. Like, an all-out makeout session in front of the fire and all the other club's members. Eventually Mycroft gives in and is willing to talk, to keep Sherlock from embarrassing him further.