"Dull but safe," he returns blandly, but smiles just a bit to show that the sins of the father are not necessarily revisited, and exchanges money for information with Mss. Blewett while Sirius heads to the back. He hadn't expected it to take more than a moment, but now she wants to tell him about all 'his cousin's' former students, and despite himself, he can't pull away from that. He's listening to what became of of Miss Bulstrode--one of his emeralds in the rough, although he'd never tell anyone such a thing outright, including her--with an increasing weight of depression when Sirius comes back.