Severus was getting "one of his heads".

It wasn't the stress of being previously subjected to a classroom full of some of the most irritating and inept students he had ever had the misfortune to teach. That was quite easily remedied with an overly large Scotch. This one was entirely his own fault. After decades of fervently subscribing to the philosophy that eavesdroppers never hear any good of themselves, he had allowed himself a momentary lapse in judgement and spied on a conversation.

Potter.

Weasley.

Granger.

Initially to her credit, Miss Granger had kept out of the conversation. But then on reflection, Severus had decided that was just as bad. Her silence somehow condoned the opinions of the two young men she was constantly attached to. He'd considered her better than that. Though he couldn't remember how he had formulated that consideration. Nor exactly when.

What had started as a below average day had rapidly degenerated into positively loathsome. Severus had felt in need of a diversion, and frightening miscreants was always a good default distraction from whatever was making life so utterly tedious at any given moment. He had swept menacingly through the corridors, only to find himself bereft of any students to punish. Until he heard voices.

He cast an amplification charm, and listened.

Greasy. Unwashed. Malodorous. A frightful sight that haunted the corridors in the dead of night getting some perverse kind of thrill out of punishing mischief makers. And of course, that would be the only thrill available as no sane woman in possession of her mental faculties, let alone functioning senses would ever look twice.

Casting a concealment charm about his person, Severus deliberately swept past the three students. Granger sat impassively as the boys continued pouring forth insults and contempt. Severus fought hard the impulse to hex all three of them seven ways to Sunday.

Being rather more astute than her constant companions, Hermione had picked up on the small waft of moving air and faint hint of the cologne that always subtly permeated the air when her Potions Master was hovering over her in class.

And while Severus spent a miserable evening sulking in his rooms like a petulant child, Hermione teasingly admonished Harry and Ron for speaking so unkindly about Filch in the corridor that afternoon.