Severus looked up from the marking he was doing when the knock came at the door. Faustus was already in his room, most likely reading before he went to bed. He'd taken himself off there shortly after Severus had finished explaining... to a certain extent... why Harry was coming over. Faustus had said wryly that Harry probably wouldn't appreciate an audience. Severus agreed with him but expected that Harry might have appreciated seeing Faustus again; he seemed to like his son.
He set his quill aside and got up, walking over and opening the door. He scowled momentarily when he saw how tired Harry looked then he stepped aside.
"Come inside," he said briskly. "You have saved me from some truly atrocious attempts at essay-writing my Fifth Years. I am left to wonder if some them have lost their grasp of the English language."