In the second book, "Harry Potter and the Chamber of Secrets", one of Voldemort's horcruxes, his childhood diary possesses the body of a girl named Ginny Weasley and lets a monster called a basilisk into the school. The basilisk petrified several Muggle-born students, turning them to stone. Harry and his friends stop it, though Harry's friend, Hermione is also petrified in the process. She did left a clue behind, and Harry destroyed the diary, restoring Ginny's vitality.