Perhaps, Severus reflects, he began this conversation with aggression because the mere idea of asking her for help turns his stomach to rot. He stares down at her impassively, his jaw tight and mouth set, certainly not revealing in his expression how he hates to humble or ingratiate himself to Hermione Granger. Or that, somewhere deep down, he might feel a sense of grudging respect for a witch who, at the age of fifteen, cast a Protean Charm flawlessly.

"And you are aware of its other uses?" he asks; his tone isn't gentle, but he's no longer interrogating her. He's being...almost conversational. Easing in to his request as best he can so he's able to wake up tomorrow without loathing himself - both for asking for her help and for dragging her a little too close to the grey area diving her (ostensibly) wholesome Hogwarts education and the Dark Arts. And, too, he doesn't want to terrify the little nuisance. He needs her, and they are discussing Dark Marks and Protean Charms.