"Mister Potter," his eyes flicked to Draco, "and Mister Malfoy. While it is not a surprise to see you together, it is a surprise to find you outside of my office," he said dryly, "You do not have an appointment, and I do not accept drop ins outside of school hours. If you wish to speak to me, I suggest you come back and make an  appointment," he annunciated the word sharply and precisely, and made to shut the door, "Good evening, gentlemen,"