At Hogwarts, Harry begins learning magical spells, plays Quidditch. One night the stair cases change paths leading Harry, Ron and Hermione to the forbidden floor of Hogwarts. There is a giant three-headed dog named Fluffy which guards the Philosopher's Stone, as it turns out later. Harry suspects that the Poisons teacher Severus Snape is trying to obtain the stone to return Voldemort to physical form. 