Christmas was coming. One morning in mid-December, Hogwarts woke to find itself covered in several feet of snow. The lake froze solid and the Weasley twins were punished for bewitching several snowballs so that they followed Quirrell around, bouncing off the back of his turban.

Harry, just go down to the lake tomorrow, right, stick your head in, yell at the merpeople to give back whatever they’ve nicked, and see if they chuck it out. Best you can do, mate.

The narrow path had opened up suddenly onto the edge of a great black lake. Perched atop a high mountain on the other side, its windows sparkling in the starry sky, was a vast castle with many turrets and towers.

Raindrops the size of bullets thundered on the castle windows for days on end; the lake rose, the flower beds turned into muddy streams, and Hagrid’s pumpkins swelled to the size of garden sheds.