Severus was not in the best of moods. It had little to do with the move back to Hogwarts. With Titchy's help, that had gone smoothly and everything was back in place, including himself and Faustus. It certainly had nothing to do with Faustus who seemed pleased to be back at Hogwarts and was now off somewhere in the castle, possibly with Ben Boot and certainly under the watchful eye of Titchy after their effort on the night of Draco's meeting.
It was the upcoming school year or rather his preparations for it. Each year he reviewed the recent literature and updated his syllabus so that he could ensure he was teaching the correct information. This was a routine task that was always made worse by having to cope with reading about the idiotic notions people came up with in his field. He was always torn between teaching the accepted methods and just throwing it all in and teaching them his versions of the potions, which were better and easier and more effective. Unfortunately nearly all of them were unpublished purely because it had just not been feasible to do such a thing while he'd been working as a spy nor was it particularly feasible now while the war was still raging. Still the idea of publishing his own book was attractive, if for no other reason than to hear the howls of anguish from his erstwhile 'colleagues' when they realised how much better his versions of their potions were.
When the knock came at the door, he was almost pleased to set aside his syllabus and answer it. He had been woring on the Fifth Year potions - he always worked backwards, from the most interesting, Seventh Year, to the least interesting, First Year - ensuring that he was covering all of the potions that would be on that year's OWL exam.
He opened the door and nodded to Theo, stepped aside to allow him to enter. "Theo," he said then gestured towards his workroom. He'd told Faustus that Theo was coming for a lesson this morning and he knew his son would remain away from their rooms until at least lunchtime.