There wasn't anything special about the third Tuesday of October. When Harry and Ron woke up that morning, nothing seemed amiss. The sky was crisp and cold outside the tower windows, and Neville's toad had escaped again. When they climbed down from the tower to search, Hermione was already deeply immersed in an inappropriately thick book in the common room. Everything seemed normal.

Yet as the day went on, things got progressively stranger.

At breakfast, the twins cast a permanent hiccuping charm on one of the Slytherin first years. Even though the girl broke into hysterical tears halfway through the kippers and had to be taken to Madame Pomfrey for a Calming Draught, there were no house points taken from Gryffindor. Professor McGonagall just sent them to class while Snape glowered and muttered under his breath.

After Charms, Malfoy and his cronies ambushed Harry in the hallway. After a brief struggle, Crabbe ended up with a bloodied nose and Malfoy went running to his head of house about 'Potter's attack.' Snape cast episkey to stop the bleeding, but said nothing about detention or Gryffindor points.

In Potions, Snape glared at them even more fiercely than usual, but said almost nothing. He simply revealed the brewing instructions on the board and retreated to his desk. When Seamus made his potion overflow and leaked viscous fluid all over the classroom, Snape merely vanished the mess.

Finally Ron leaned over and whispered, "What d'you think's the matter with Snape?"

Harry shrugged, wondering that himself. He looked to Hermione for an explanation, but she was focused on Snape, considering.

"Dunno. Maybe he's not really Snape. Polyjuiced, or something."

Ron stared, and Snape scowled back. "Nah. Seems like Snape to me. Just... not as Snape as usual."

"I don't think he can punish us." They stared at Hermione, shocked.

"But-"

"I don't know why, but I'm sure that's it."

Harry and Ron sat in awed silence, considering the possibilities. Hermione, looking alarmed, hissed a warning, which they ignored.

Calmly, deliberately, Harry tipped his cauldron forward and dumped the contents on Draco. Ignoring the spluttering boy, he smiled serenely at Snape, who did absolutely nothing.

Harry and Ron went to the other Gryffindor table, where Dean, Seamus and Neville were still trying to fix the slowly overflowing potion. In hushed tones, they told them the news. Seamus and Dean were as amazed as they'd been, but Neville looked unaccountably smug.

"I overheard Professors Sprout and Flitwick talking. McGonagall bet him that he couldn't go a day without docking points from Gryffindor."

They sat in stunned silence, while Hermione industriously stirred her potion in the background, ignoring them. It was Ron who eventually broke the silence.

"Blimey! You waited 'till now to tell us?"