There's something off about this, something Severus can't quite put his finger on. A normal person might just shrug it off as being uncomfortable with confrontation from transients, but Severus is not a normal person. He is a very paranoid, grudging person with an uncanny sixth sense for the fantastic, and so the instant the shuffling panhandler meets his gaze, he reaches out. (Not with his hands.)

He speaks no incantation, twitches no wand, but if Sebastian is looking close enough he might notice the tell-tale sharp and brief frown of someone casting a spell. In a heartbeat, Severus is invading the mind of the man who's approached them, lance-like and brutal, searching-