Chapter 1: I Accidentally Vaporize My Pre-Algebra Teacher
Percy Jackson introduces himself as a troubled twelve-year-old at Yancy Academy. On a field trip to the Metropolitan Museum of Art, his Latin teacher Mr. Brunner quizzes him on Greek mythology while his pre-algebra teacher Mrs. Dodds watches menacingly. When Percy accidentally pushes a bully into a fountain, Mrs. Dodds lures him inside the museum and transforms into a monstrous Fury, attacking him. Mr. Brunner tosses Percy a pen that becomes a bronze sword, and Percy vaporises her.
Afterward, nobody remembers Mrs. Dodds ever existing, except Grover Underwood, who acts nervous and evasive. Percy is left confused and disturbed, unsure whether he imagined the entire encounter.
Chapter 2: Three Old Ladies Knit the Socks of Death
Percy's strange experiences continue as the entire school pretends Mrs. Dodds never existed. His grades slip and he gets expelled from Yancy Academy. On the last day, he overhears Grover and Mr. Brunner discussing his safety and a summer solstice deadline.
On the bus ride home, Percy confronts Grover about what he heard. At a roadside stop, three old ladies - the Fates - knit an enormous pair of socks and cut the yarn while staring at Percy. Grover is terrified, believing this is a death omen.
Percy arrives home to his mother Sally Jackson and her awful husband Gabe Ugliano. Sally takes Percy on a trip to their cabin at Montauk beach, where she tells him about his father - a man she met one summer who was lost at sea.
That night, Grover arrives during a terrible storm, revealing his true form as a satyr with furry legs and hooves. He warns that something is pursuing Percy.
Percy, his mother Sally, and Grover flee through the storm toward Camp Half-Blood. Their car is struck by lightning and wrecked. The Minotaur pursues them up Half-Blood Hill. Sally is seized by the monster and dissolves into golden light before Percy's eyes.
Fuelled by rage, Percy breaks off the Minotaur's horn and drives it into the monster, destroying it. He collapses at the farmhouse porch, where he glimpses a bearded man and a blond girl - Annabeth Chase - before losing consciousness.
Percy wakes at Camp Half-Blood, tended by Annabeth and Grover. On the farmhouse porch he meets Mr. D (Dionysus), the camp director, and discovers that Mr. Brunner is actually Chiron, the immortal centaur trainer of heroes.
Chiron explains that the Greek gods are real, still alive, and now centred in America. Percy is a half-blood - the child of a mortal and a god. Dionysus demonstrates his divine power, and Chiron reveals his true centaur form.
Chiron gives Percy a tour of Camp Half-Blood. Annabeth explains the cabin system and reveals she is a daughter of Athena. Percy is placed in the overcrowded Hermes cabin where he meets counsellor Luke Castellan, a friendly older camper with a scar on his face.
Percy also encounters Clarisse, daughter of Ares, who tries to dunk his head in a toilet. Percy instinctively causes the plumbing to explode, soaking Clarisse and impressing Annabeth, who wants him on her capture-the-flag team.
Percy settles into camp life, taking lessons in Ancient Greek from Annabeth and sword fighting from Luke. He struggles with most activities but discovers a natural talent with a sword, even disarming Luke during practice.
At dinner, Percy learns about burned offerings to the gods and silently pleads for his unknown father to claim him. Grover tells Percy about Thalia, daughter of Zeus, who sacrificed herself to save Luke, Annabeth, and Grover, and was turned into the pine tree that protects the camp's borders.
During capture the flag, Percy is stationed at the creek as bait. Clarisse and her Ares cabin mates attack him, but Percy discovers that water heals him and enhances his strength. He defeats them all and Luke captures the enemy flag.
A hellhound attacks Percy, but Chiron destroys it with arrows. As Percy stands in the creek, a glowing green trident appears above his head - the symbol of Poseidon. He is claimed as a son of the sea god, shocking the entire camp.
Percy is moved to Cabin Three and isolated from the other campers. Chiron summons him to discuss the stolen lightning bolt of Zeus. The gods believe Percy, as Poseidon's son, stole the master bolt during the winter solstice. Percy must go on a quest to the Underworld to recover the bolt before the summer solstice or war will break out among the gods.
Percy consults the Oracle, which delivers a prophecy about going west to face a god who has turned, being betrayed by a friend, and failing to save what matters most. He chooses Annabeth and Grover as his companions.
Luke gives Percy a pair of magic flying shoes as a going-away gift. Chiron presents Percy with Riptide, a celestial bronze sword disguised as a pen that always returns to his pocket. Percy gives the flying shoes to Grover since flying would be dangerous for a son of Poseidon.
The trio departs for Manhattan by van, then boards a Greyhound bus. Three Furies, including the returned Mrs. Dodds, ambush them. Percy uses Annabeth's invisibility cap to escape, but the bus is destroyed by lightning. They flee into the New Jersey woods.
Wandering through New Jersey, Percy, Annabeth, and Grover stumble upon Aunty Em's Garden Gnome Emporium. The kindly-seeming proprietor feeds them burgers and tries to pose them for a photo. Grover recognises that the lifelike statues are petrified people, and Annabeth realises their host is Medusa.
Percy fights Medusa using a glass gazing ball to track her reflection, and beheads her with Riptide. He defiantly mails her head to Mount Olympus with his name on the package.
Percy, Annabeth, and Grover camp in the woods, where Percy has disturbing dreams of a voice from a dark pit urging him to bring the master bolt to the Underworld. Grover talks about his dream of finding the great god Pan and his quest for a searcher's licence.
In the morning, Grover befriends a runaway pink poodle named Gladiola. They return the dog for the reward money and use it to buy Amtrak tickets heading west toward Denver.
On the train west, Annabeth shares her painful backstory - abandoned by her father at seven, she ran away and was found by Thalia and Luke. During a layover in St. Louis, they visit the Gateway Arch, where Percy is attacked by the Chimera and its mother Echidna.
Poisoned and cornered at the top of the Arch, Percy leaps into the Mississippi River far below. The water heals him, and a Nereid messenger from Poseidon tells him to go to Santa Monica beach before entering the Underworld.
Percy surfaces from the Mississippi and reunites with Annabeth and Grover amid the chaos of a national news story. Percy is now being portrayed as a fugitive wanted by police. They narrowly escape the scene and catch their train onward to Denver.
Percy becomes a media sensation - his stepfather Gabe is giving interviews, and Percy's photo is in newspapers across the country.
In Denver, the trio uses an Iris-message to contact Luke at camp and learn that tensions between the cabins are rising. At a diner, Ares appears in person and offers Percy a deal: retrieve his shield from an abandoned water park and he will provide information about Percy's mother and a ride west.
Percy and Annabeth enter the Tunnel of Love ride and spring a trap set by Hephaestus - a net of golden cables and an army of mechanical spiders, all broadcast live to Olympus. They escape using Percy's water powers just before the cameras roll.
Percy confronts Ares and returns the shield. Ares reveals that Percy's mother is alive - held hostage, not dead. He provides them a ride west in an animal smuggling truck. Percy, Annabeth, and Grover free the mistreated animals - a zebra, a lion, and an antelope - when the truck stops in Las Vegas.
They wander into the Lotus Hotel and Casino, a magical trap where time passes unnoticed. Five days vanish in what feels like hours. Percy snaps them out of the trance just in time - they have only one day left before the summer solstice.
The trio races to Los Angeles by taxi, using their Lotus Casino credit card. Percy wades into the Pacific at Santa Monica, where a Nereid from Poseidon's court gives him three magic pearls for escaping danger and warns him not to trust gifts.
In West Hollywood, they find DOA Recording Studios, the entrance to the Underworld, after surviving an encounter with Procrustes the Stretcher at Crusty's Water Bed Palace.
Percy, Annabeth, and Grover enter the Underworld lobby and bribe Charon the ferryman with golden drachmas. They cross the River Styx and pass through the gates of Erebus. Annabeth tames the three-headed dog Cerberus using a red rubber ball and obedience commands.
They explore the Fields of Asphodel and glimpse both the punishments of the damned and the paradise of Elysium. Heading toward Hades's palace, Grover's flying shoes suddenly drag him toward Tartarus. They barely rescue him from the edge of the bottomless pit, where an evil voice chants ancient magic.
In the throne room of Hades, Percy discovers that the master bolt has been in his backpack all along - planted there by magic. Hades is furious, accusing Percy of stealing both the bolt and his own Helm of Darkness. Percy realises they have all been manipulated by a third party.
Hades reveals Percy's mother, trapped in golden light. He offers to trade her for the bolt. Percy must choose between his mother and his friends - there are only three pearls. He uses them to escape with Annabeth and Grover, leaving his mother behind, fulfilling the prophecy's bitter final line.
Percy confronts Ares on the Santa Monica beach, realising the god of war orchestrated the theft, acting as a pawn for the voice in the pit. Ares had planted the master bolt in the backpack, timed to appear only in the Underworld.
Percy fights Ares in an epic duel on the surf, wounding the god in the heel with Riptide. A dark presence stops Ares from killing Percy. The Furies appear and Percy gives them Hades's Helm of Darkness to return. He catches a flight to New York to deliver the bolt to Zeus before the deadline.