In full, the film is a race to protect a magical object from a thief, and the thief turns out to be someone other than the obvious suspect. Harry has been raised by relatives who hid his magical heritage from him, and Hagrid rescues him from them and brings him into the wizarding world.
At Hogwarts, Harry is sorted into Gryffindor and becomes friends with Ron and Hermione, while he clashes with the rival student Draco Malfoy. The three friends discover that a three headed dog is guarding a trapdoor in a forbidden corridor. They learn that the dog is protecting the sorcerer's stone, an object that can give its owner endless life. Meanwhile Harry joins the house Quidditch team as Seeker, and he comes to suspect that the stern teacher Snape wants to steal the Stone.
When Dumbledore is called away from the school, the three friends decide to reach the Stone first. They get past a series of magical traps, including a giant living chess game, and Ron and Hermione are left behind along the way. Harry goes on alone and finds Professor Quirrell waiting, not Snape. Quirrell is carrying Voldemort's weakened spirit on the back of his head.
The Stone is hidden in an enchanted mirror, and Harry wins it because he only wants to find it, not to use it. Quirrell is hurt when he touches Harry, and Voldemort's spirit flees. Harry wakes in the hospital wing, where Dumbledore tells him the Stone has been destroyed and that his mother's love protected him. Gryffindor wins the House Cup, and Harry heads home for the summer.