Harry Potter and the Problem of Potions
Once upon a time, Harry Potter hid for two hours from Dudley in a chemistry classroom, while a nice graduate student explained about the scientific method and interesting facts about acids. A pebble thrown into the water causes ripples.
Contains, in no particular order: magic candymaking, Harry falling in love with a house, evil kitten Draco Malfoy, and Hermione attempting to apply logic to the wizarding world.