Regulus didn't know how she'd managed to capture Sirius's attention in such a short amount of time. He didn't know why she'd to all appearances cut him off. No one had ever done that, and Sirius didn't know how to deal with it. Entertaining as it was to watch him, Regulus couldn't help but worry. They were dealing with a girl who'd broken into the most secure place in the world and stolen an ancient artifact, incurring the wrath of the Dark Lord. Beyond that, no one knew why she'd come to Hogwarts six years late. Regulus hadn't ever heard of that happening before. Everyone had a theory, and none of them were innocent. Exactly what sort of person was Hermione Granger? Would he want to allow his brother to be exposed to the dangers of associating with her?