Percy Jackson has been invited to Goode High School by Paul Blofis, his mom's new boyfriend. While at the freshmen orientation Percy has a run in with Rachel Elizabeth Dare, the mysterious mortal he met the previous winter at the Hoover Dam who can see through the Mist, and two demonic cheerleaders, (empousai). He's able to defeat one of the empousai, Tammi, but the other, Kelli, after bursting in to flames, escapes, getting Percy in trouble yet again. With Rachel's help, he's able to get out of the school, and escape the cops. While running from Goode, he runs into Annabeth, a fellow demigod who is a daughter of Athena. They were supposed to go to a movie and hang out together, but their afternoon was canceled (hence, Percy's run in with the cheerleaders) because they need to get him to Camp Half-Blood before the mortal cops find him, or worse, other monsters. They head for Camp Half-Blood, and ride in silence.
Upon their arrival, Percy discovers Dionysus' absence and he attends Grover's hearing with the Council of Cloven Elders, who feel that they should revoke his searcher's license since he has found no evidence of hearing Pan's voice after six months of claiming to hear him. Also in attendance, Grover's new girlfriend Juniper, a dryad. Juniper greatly cares for Grover, and is against The Cloven Elders. They give him one week to find proof of Pan's existence. Percy also meets the new swordsman trainer, Quintus, an adult Half-Blood (a son of Athena) and his gigantic pet hellhound, Mrs. O'Leary.
As Luke's forces are gathering and plan to invade Camp Half-Blood, the demigods begin preparations to repel the attack. While training with giant scorpions, Percy and Annabeth discover an entrance into the dangerous Labyrinth. The entrance is a set of boulders named Zeus's Fist because it looks like a fist. They realize Luke's plan to invade camp through the Labyrinth. Clarisse's mission from last winter is discovered to have been scouting around one of the entrances in Phoenix, Arizona, because her mom finds a fellow Half-Blood near her house, Chris Rodriguez, who'd been driven insane in the Labyrinth.
Annabeth is chosen to the lead the quest to find the workshop of Daedalus, inventor of the Labyrinth and holder of Ariadne's string, and consults the Oracle. She breaks the rules by allowing three people to accompany her on her quest: Percy, Tyson, and Grover to come with her. This opposes the ancient laws because three is a sacred number (three Furies, Fates, etc). She goes to see the oracle and when she comes back, she tells the war council(the counselor of each cabin, Chiron, and Quintus)the prophecy: You shall delve in the darkness in the endless maze. The dead, the traitor, and the lost one raise. You shall rise or fall by the ghost king's hand. The child of Athena's final stand. Destroy with a hero's final breath... She doesn't say the last line. Annabeth said she "forgot" it, but Chiron, Percy, and others are suspicious that Annabeth is hiding something because she almost never forgets what she hears. Later that night, Percy receives a mysterious Iris message that shows Nico talking to a ghost adviser, and raising the dead to get answers to find a way to trade a soul for a soul. Before descending into the Labyrinth, Quintus gives Percy a dog whistle, that when blown, will summon Mrs. O'Leary to him whenever he is in trouble, but Percy says that he will not use the whistle because Juniper tells Percy not to trust Quintus, since she saw him near the Labyinth entrance.
Once in the Labyrinth, they immediately get lost and don't know which way to turn. They meet Janus, the two-faced god of choices, and Hera, Queen of Olympus and the goddess of marriage. Hera guides them and tells them to seek out Hephaestus, who might have kept track of Daedalus over the ages. They continue their journey through the maze and come out into Alcatraz, which was currently being used to keep in a Hecatonchires (or Hundred-Handed One), Briares. who were allies to the Olympians during the first war. Tyson meets his hero, the Hundred-Handed One, Briares, and sets him free, only to discover that he lost his will and confidence for battle. They face Kampê, who nearly kills Tyson, but manage to escape.
They soon come across the demonic Triple G Ranch and meet Geryon and Eurytion, an elder son of Ares. Staying there also is Nico, the son of Hades. Geryon was paid to let Annabeth and her friends go through, but not Nico. Percy makes a deal that if he cleaned the stables of Diomedes like Hercules did, then Geryon would let his friends go. He succeeds by using the power of the ocean inside him, but Geryon tells him that he didn't bind the deal with something such as swearing on the River Styx. Percy and Geryon engage in a serious battle. Percy learns that Geryon has three hearts and can not defeat him with a sword. He gets a bow and prays to Artemis and Apollo to help him shoot. He succeeds and hits all 3 hearts. He sets Eurytion free of his command by killing Geryon. For his thanks, he gives them a silver disk necklace that would help locate the god Hephaestus. Afterwards, Nico summons Bianca's spirit, who lets him know that Percy wasn't to blame for her death. Nico decides to remain behind at the ranch, while the others continue.
As they continue their quest to find Hephaestus, they come across the Sphinx. They escape the grasp of the Sphinx and discover Hephaestus in one of his forges. He tells them that he'll help them find Daedalus if they found out whose been using his forge at Mount St. Helens. They agree, but split up along the way when Grover gets a scent of Pan. Tyson decides to go with him, leaving Percy and Annabeth to head to the forge. They discover telekhines (sea demons) there, making a weapon for Kronos. Percy tells Annabeth to escape while she can. She kisses him for luck and they part ways.
The telekhines discover Percy and throw lava on him. Percy summons all his powers to get rid of the lava and the telekhines, and ends up causing Mount St. Helens to erupt and almost awaken Typhon, one of the worst monsters of all. He is then sent while unconscious to Calypso's island by Hera. Calypso tells Percy that every hero sent to her island is someone who she can't resist falling in love with. Hephaestus arrives and tells him what he wants to know about Daedalus and what he'll need to guide him through the Labyrinth: Rachel Elizabeth Dare. Calypso offers him to stay, and she tells him her curse; 'the Fates make sure the gods send her a hero that she can't help but fall in love with and it's a hero who can never stay'. He leaves Calypso's island and heads for camp, stating that he would be thinking about her for the rest of his life. He and Annabeth go looking for Rachel and find her in Manhattan.
Together, they descend into the Labyrinth again, this time with Rachel as their guide, whose eyes are harder to fool since she can see directly through the Mist. They find an underground arena with Luke's troops in it, being used to entertain a giant son of Poseidon and Gaea, Antaeus. Percy duels against a dracaena, who he easily defeats, and then fights a Half-Blood named Ethan Nakamura, who he spares in the battle. He then challenges Antaeus to battle and successfully kills him. The monsters begin to overwhelm them and he calls Mrs. O'Leary by use of the dog whistle to help them out. They escape and finally find their way to Daedalus' workshop to discover Daedalus is actually Quintus. Daedalus had built five bodies for himself over the millennium, by casting his soul into the humanoid automatons. Monsters attack again in his workshop, led by Kelli who has taken Nico captive. He had left the Labyrinth, but he was advised by Minos to return because Minos said Percy and Annabeth would be in danger. It was a trick , because Minos wanted revenge on Daedalus for his treachery and giving the daughters of a rival king the tools to kill him. He reveals that once Nico got the soul, he would use it for himself, and not on Bianca. Percy, Annabeth, Nico and Rachel are able to escape on bronze wings and fly out of Daedalus's workshop, leaving him to battle the monsters with Mrs. O'Leary.
Rachel convinces a chauffeur to drive them into the city and she spots another entrance to the Labyrinth in a museum. Once in the Labyrinth, they come across a tunnel that leads to Mount Tamalpais and the palace of Kronos. Percy can't help but check it out and discovers the telekhines from Hephaestus' forge have reforged the weapon for the Lord of Time Kronos, his scythe or sickle. Percy opens the coffin to discover Luke, who looks dead. Ethan, son of Nemesis (a minor goddess), enters with the telekhines and pledges his allegiance to Kronos. That was the last soul Kronos needed to complete his transformating body, and he is resurrected in the form of Luke's body. Percy and his friends barely escape, and Nico uses his powers to cause the ceiling of the palace to cave in.
They continue on their journey back to New York and begin to sense something ancient and powerful in another tunnel. They find Tyson and Grover, and discover the lost god Pan in a crystal cavern. He wants Grover to tell the world he has died, since his kingdom has faded and that his spirit shall live inside all of them. He leaves Percy, Annabeth, and Rachel cryptic messages about their futures. Pan then dies and the crystal cavern vanishes along with its extinct wonders. They then return to camp, where Luke's forces have begun the invasion. They're able to beat them back, with the help of Grover, who creates panic among the enemy forces, but have a few casualties. After the battle, Daedalus, decides that the way to the camp must be sealed so that Kronos' armies can not enter. Nico, being a son of Hades, releases his soul and Daedalus finally finds peace resulting in the destruction of the Labyrinth.
The Council of Cloven Elders decide that Grover should be exiled and that the search for Pan should continue, but Dionysus returns and outvotes them. Percy hears the last line of Annabeth's prophecy and is upset to hear that she would Lose a love to worse than death, wasn't about him as she had thought, but Luke. Percy wants to tell Annabeth that he doesn't want to be so distant from her, but finds that he can't. Annabeth decides to stay at camp a while and Percy heads home to celebrate his fifteenth birthday with his mom, Paul Blofis, and Tyson. He gets a surprise visitor in the form of Poseidon, who gives him a sand dollar as a birthday gift. He also gives him a warning that ancient forces are stirring, the great monster Typhon is stirring from his imprisonment under Mount St. Helens due to the Titans' rising and Percy's outburst. Poseidon then tells Percy that he is his favorite son. Also, Paul tells Percy that he wants to propose to his mom. Percy plants a moonlace flower on his fire escape that he'd kept from Calypso's island and finds Nico there. Nico tells Percy that he has some news and a way to beat Luke, but gets distracted when he sees the blue birthday cake. Percy invites him in to eat after suspecting that Nico has never had his own birthday cake before.
source: Wikipedia
