WHO: Everyone
WHAT: A catastrophe
WHERE: St. Mungo's
WHEN: Thursday Afternoon, around 4:45p

The bottle had been swapped the night before. The intern, a young wizard named Julius Young, was not supposed to be using Draco's ingredients, but he'd run out of his own and didn't want to wait till tomorrow. He was almost done, fifteen minutes before his shift was over. Arsenius had gone home. Draco was on break. He charmed the lock open, took out the bottle, and went back to his work station.

It was one of the most common potions the hospital used, but one of the ingredients, if mixed with Salamander Blood, was horribly explosive. The night before someone had sneaked in to the lab and swapped the bottle with salamander blood, dissolved in water with green dye. When the fake ingredient hit the half-finished potion, there was a shower of sparks, and then--as it mixed in-- a big bang.

The hospital shook, the blast set off a chain reaction of other, less stable ingredients in the lab. The floor above caved into the lab below. The lab sank into the floor below. Clocks fell off the wall, bottles rattled off the edges of tables.

The hospital broke into a state of panic.