Harry Potter is still living with his Aunt Petunia, Uncle Vernon Dursley, and their son, Dudley Dursley. For two years, he has lived with them knowing that he is a wizard; he then goes to Hogwarts School for Witchcraft and Wizardry for his third year, as he meets Sirius Black, and Professor Remus Lupin, who happens to be a werewolf. When he goes to the Leaky Cauldron, he finds out that dementors are around. 

The third Leaky Cauldron Harry Potter fantasy novel.