A few weeks later, while relaxing after the end-of-session examinations, Harry suddenly wonders how something as illegal as a dragon's egg came into Hagrid's possession. The gamekeeper says he was given it by a hooded stranger who bought him several drinks and asked him how to get past the three-headed dog, which Hagrid admits is easy – music sends it to sleep. Realising that one of the Philosopher's Stone's defences is no longer secure, Harry goes to inform Professor Dumbledore, only to find that the headmaster has just left for an important meeting. Harry concludes that Snape faked the message that called Dumbledore away and will try to steal the Stone that night.
Covered by the Invisibility Cloak, Harry and his two friends go to the three-headed dog's chamber, where Harry sends the beast to sleep by playing a flute. After lifting the trap-door, they encounter a series of obstacles, each of which requires special skills possessed by one of the three, and one of which requires Ron to sacrifice himself. In the final room Harry, now alone, finds Quirrell rather than Snape. Quirrell admits that he let in the troll that tried to kill Hermione in the toilet, and that he tried to kill Harry during the first Quidditch match but was knocked over by Hermione. Snape had been trying to protect Harry and suspected Quirrell. Quirrell serves Voldemort and, after failing to steal the Philosopher's Stone from Gringotts, allowed his master to possess him in order to improve their chances of success. However the only other object in the room is the Mirror of Erised, and Quirrell can see no sign of the Stone. At Voldemort's bidding, Quirrel forces Harry to stand in front of the Mirror. Harry feels the Stone drop into his pocket and tries to stall. Quirrell removes his turban, revealing the face of Voldemort on the back of his head. Voldemort/Quirrell tries to grab the Stone from Harry, but simply touching Harry causes Quirrell's flesh to burn. After further struggles Harry passes out.
He awakes in the school hospital, where Professor Dumbledore tells him that he survived because his mother sacrificed her life to protect him, and Voldemort could not understand the power of such love. Voldemort left Quirrell to die, and is likely to return by some other means. Dumbledore had foreseen that the Mirror would show Voldemort/Quirrell only themselves making the elixir of life, as they wanted to use the Philosopher's Stone; Harry was able to see the Stone in the Mirror because he wanted to find it but not to use it. The Stone has now been destroyed.
Harry returns to the Dursleys for the summer holiday, but does not tell them that under-age wizards are forbidden to use magic outside Hogwarts.
