Harry Potter and the Chamber of Secrets

A warning appears in blood on the castle walls: the Chamber of Secrets has been opened. Students are petrified, including Hermione and Colin Creevey, and the school suspects Harry because he is a Parselmouth. The heir is Tom Riddle, preserved in a diary that possesses Ginny Weasley. Harry enters the Chamber, kills the basilisk with the Sword of Gryffindor, and destroys the diary with a fang. That diary was a Horcrux. Gilderoy Lockhart loses his memory to his own broken spell, and Lucius Malfoy loses his house-elf.