Harry Potter and the Half-Blood Prince
The Death Eaters all escape afterwards. Harry tries to get Snape, but Snape is too fast. When Harry tries to use some curses he found in the Half-Blood Prince's book, Snape fights back and then declares that he is the Half-Blood Prince. Later, Hermione says this is true, having found a newspaper article about a girl named Eileen Prince (a witch) marrying a man named Tobias Snape (a Muggle), making Snape a half-blood wizard.