Harry Potter and the Chamber of Secrets

Harry returns for his second year at Hogwarts against the warnings of a self-punishing house-elf, and the school soon turns against him. A voice in the walls, messages written in blood, and a legend about a hidden chamber all point toward a monster loose in the castle. Rowling deepens the series here, planting the diary of Tom Riddle, whose importance only becomes clear books later. Harry learns that the history of Hogwarts is darker than his first year ever suggested.