Just before the start of the novel, Voldemort, the most powerful Dark wizard in history, killed Harry's parents but mysteriously vanished after trying to kill Harry. While the wizarding world is celebrating Voldemort's downfall, Professor Dumbledore, Professor McGonagall and Hagrid place the one year-old orphan in the care of his Muggle (non-wizard) aunt and uncle, Vernon and Petunia Dursley. For ten years, they and their son Dudley bully Harry. Shortly before Harry's eleventh birthday, a series of letters addressed to Harry arrive, but Vernon destroys them before Harry can read them. To get away from the letters, Vernon takes the family to a lonely island. As they are settling in, Hagrid bursts through the door to tell Harry what the Dursleys have kept him from finding out: Harry is a wizard and has been accepted at Hogwarts.
Hagrid takes Harry to Diagon Alley, a magically-concealed shopping precinct in London, where Harry is bewildered to discover how famous he is among wizards as "the boy who lived." He also finds that he is quite wealthy, since a bequest from his parents has remained on deposit at Gringotts Wizarding Bank. Guided by Hagrid, he buys the books and equipment he needs for Hogwarts. At the wand shop, he finds that the only wand that works well for him is the twin of Voldemort's - both wands contain feathers from the same phoenix. A month later, Harry leaves the Dursleys' home to catch the Hogwarts Express from King's Cross railway station. There he meets the Weasley family, who show him how to pass through the magical wall to Platform 9¾, where the train is waiting. While on the train Harry makes friends with Ron Weasley, who tells him that someone tried to rob a vault at Gringotts. Another new pupil, Draco Malfoy, accompanied by his sidekicks Vincent Crabbe and Gregory Goyle, offers to advise Harry, but Harry dislikes Draco's arrogance and prejudice. Before the term's first dinner in the school's Great Hall, the new pupils are allocated to houses by the magical Sorting Hat. When it is Harry's turn to be sorted, the Hat wonders whether he should be in Slytherin, but when Harry objects, the Hat sends him to join the Weasleys in Gryffindor. While Harry is eating, Professor Snape catches his eye and Harry feels a sudden stab of pain in the scar Voldemort left on his forehead.
After a horrible first Potions lesson with Snape, Harry and Ron visit Hagrid, who lives in a rustic house on the edge of the Forbidden Forest. There they learn that the attempted robbery at Gringotts happened the day Harry withdrew money. Harry remembers that Hagrid had removed a small package from the vault that was broken into and searched.
During the new pupils' first broom-flying lesson, Neville Longbottom breaks his wrist, and Draco takes advantage to throw the forgetful Neville's fragile Remembrall high in the air. Harry gives chase on his broomstick, catching the Remembrall inches from the ground. Professor McGonagall dashes out and appoints him as the new Seeker for the Gryffindor Quidditch team. [1] When Draco tricks Ron and Harry, accompanied by Neville and the bossy Hermione Granger, into a midnight excursion, they accidentally enter a forbidden corridor and find a huge three-headed dog. The group hastily retreats, and Hermione notices that the dog is standing over a trap-door. Harry concludes that the monster is guarding the package Hagrid retrieved from Gringotts.
After Ron criticizes Hermione's ostentatious proficiency in Charms, she hides in tears in the girls' toilet. Professor Quirrell reports that a troll has entered the dungeons. While everyone else returns to their dormitories, Harry and Ron rush to warn Hermione. The troll corners Hermione in the toilet but when Harry sticks his wand up one of its nostrils, Ron uses the levitation spell to knock out the troll with its own club. Afterwards, several professors arrive and Hermione takes the blame for the battle and becomes a firm friend of the two boys.
The evening before Harry's first Quidditch match, he sees Snape receiving medical attention from Filch for a bite on his leg by the three-headed dog. During the game, Harry's broomstick goes out of control, endangering his life, and Hermione notices that Snape is staring at Harry and muttering. She dashes over to the Professors' stand, knocking over Professor Quirrel in her haste, and sets fire to Snape's robe. Harry regains control of his broomstick and catches the Golden Snitch, winning the game for Gryffindor. Hagrid refuses to believe that Snape was responsible for Harry's danger, but lets slip that he bought the three-headed dog, and that the monster is guarding a secret that belongs to Professor Dumbledore and someone called Nicolas Flamel. Harry and the Weasleys stay at Hogwarts for Christmas, and one of Harry's presents, from an anonymous donor, is an Invisibility Cloak. Harry uses the Cloak to search the library's Restricted Section for information about the mysterious Flamel, has to evade Snape and Filch after an enchanted book shrieks an alarm, and slips into a room containing the Mirror of Erised, which shows his parents and several of their ancestors. Harry becomes addicted to the Mirror's visions and is rescued by Professor Dumbledore, who explains that it shows what the viewer most desperately longs for. When the rest of the pupils return for the next term, Draco plays a prank on Neville, and Harry consoles Neville with a sweet. The collectible card wrapped with the sweet identifies Flamel as an alchemist. Hermione soon finds that he is a 665-year-old man who possesses the only known Philosopher's stone, from which can be extracted an elixir of life. A few days later Harry notices Snape sneaking towards the outskirts of the Forbidden Forest. There he half-hears a furtive conversation about the Philosopher's Stone, in which Snape asks Professor Quirrell if he has found a way past the three-headed dog and menacingly tells Quirrell to decide whose side he is on. Harry concludes that Snape is trying to steal the Stone and Quirrell has prepared a series of defences for it.
The three friends discover that Hagrid is raising a baby dragon, which is against wizard law, and arrange to smuggle it out of the country around midnight. Draco arrives, hoping to raise the alarm and get them into trouble, and Neville comes to warn them of Draco's mischief. Although Ron is bitten by the dragon and is sent to the infirmary, Harry and Hermione spirit the dragon safely away. However, they are caught, and Harry loses the Invisibility Cloak. As part of their punishment, Harry, Hermione, Draco and Neville are compelled to help Hagrid to rescue a badly-injured unicorn in the Forbidden Forest. They split into two parties, and Harry and Draco find the unicorn dead, surrounded by its blood. A hooded figure crawls to the corpse and drinks the blood, while Draco screams and flees. The hooded figure moves towards Harry, who is knocked out by an agonising pain spreading from his scar. When Harry regains consciousness, the hooded figure has gone and a centaur, Firenze, offers to give him a ride back to the school. The centaur tells Harry that drinking a unicorn's blood will save the life of a mortally injured person, but leave them only barely alive. Firenze suggests Voldemort drank the unicorn's blood to gain enough strength to make the elixir of life from the Philosopher's Stone, and regain full health by drinking that. On his return, Harry finds that someone has slipped the Invisibility Cloak under his sheets.
