Harry Potter and the Philosopher's Stone is the first novel in the series and introduces the wizarding world. The story begins with Harry Potter, an orphaned boy living a miserable existence with his abusive aunt and uncle, the Dursleys. On his eleventh birthday, his life is turned upside down when Rubeus Hagrid, the groundskeeper of Hogwarts School of Witchcraft and Wizardry, reveals that Harry is a wizard and that his parents were murdered by the dark wizard Lord Voldemort. Harry travels to Hogwarts, where he is sorted into Gryffindor house and befriends Ron Weasley and Hermione Granger. Throughout his first year, the trio navigates school life, learning magic, playing Quidditch, and uncovering a plot to steal the Philosopher's Stone, a legendary object that grants immortality, hidden within the school's walls. Their investigation leads them to a confrontation with Professor Quirrell, who is secretly hosting the weakened spirit of Lord Voldemort.
The novel begins with the Dursleys of number four, Privet Drive, discovering strange occurrences, culminating in the arrival of an infant Harry Potter on their doorstep, left there by Albus Dumbledore, Professor McGonagall, and Rubeus Hagrid. For ten years, Harry lives an oppressed life, unaware of his magical heritage. Shortly before his eleventh birthday, letters addressed to him from Hogwarts begin to arrive, which the Dursleys desperately try to prevent him from reading. Their attempts to flee the letters fail, and on Harry's birthday, Hagrid arrives to deliver the letter in person and reveals Harry's identity as a wizard. Hagrid takes Harry to Diagon Alley to purchase his school supplies. Harry learns of his fame and the fortune his parents left him in a vault at Gringotts Wizarding Bank. He buys his school robes, books, a cauldron, and most importantly, his wand from Mr. Ollivander, which is revealed to be the “brother” to Lord Voldemort's wand. Hagrid also gifts Harry a snowy owl, whom he names Hedwig. Harry travels to Hogwarts via the Hogwarts Express from Platform Nine and Three-Quarters, where he meets Ron Weasley and Hermione Granger. Upon arrival, the first-year students are sorted into one of four houses by the Sorting Hat; Harry, Ron, and Hermione are all placed in Gryffindor. Harry quickly finds a rival in Draco Malfoy, a student sorted into Slytherin. Life at Hogwarts is filled with wonder and challenges, from Potions classes with the hostile Professor Snape to learning to fly on a broomstick, a skill that gets him a spot on the Gryffindor Quidditch team as their new Seeker. On Hallowe'en, the trio battles a mountain troll let into the castle, solidifying their friendship. Harry, Ron, and Hermione become suspicious of Professor Snape's behaviour and believe he is trying to steal the Philosopher's Stone for Lord Voldemort. They discover a three-headed dog, Fluffy, guarding a trapdoor and deduce it is protecting the stone. After learning that Hagrid accidentally told a stranger how to bypass Fluffy, the trio decides to intervene. They overcome a series of magical obstacles designed by the Hogwarts professors: a patch of Devil's Snare, a room of flying keys, a giant game of Wizard's Chess, and a logic puzzle with potions. Harry proceeds alone to the final chamber, where he finds not Snape, but Professor Quirrell. Quirrell reveals he was the one who let in the troll and tried to kill Harry during a Quidditch match. He reveals the back of his head, where the face of Lord Voldemort is parasitically attached. Voldemort has been using Quirrell to try and regain a body by using the Stone. The Mirror of Erised stands in the chamber, and when Harry looks into it, the Philosopher's Stone magically appears in his pocket. Quirrell attacks him, but his skin burns upon contact with Harry. Harry passes out from the pain in his scar. He awakens in the hospital wing, where Albus Dumbledore explains that Harry was protected by his mother Lily's sacrificial love, a magic that Voldemort cannot understand or touch. Dumbledore also reveals that he and the Stone's creator, Nicolas Flamel, have decided to destroy it. At the end-of-year feast, Gryffindor is awarded the House Cup, and Harry returns to Privet Drive for the summer.