[Book 2] In Anna's second year at Hogwarts School of Witchcraft and Wizardry, a series of messages on the walls of the school's corridors warn that the "Chamber of Secrets" has been opened and that the "heir of Slytherin" would kill all pupils who do not come from all-magical families. These threats are found after attacks that leave residents of the school petrified. Throughout the year, Anna and her friend Rose investigate the attacks.