- This article is about the book. For the actual battle, see Battle of the Labyrinth.
The book begins with Percy Jackson going to a freshmen orientation class at Goode High School, a school where Paul Blofis, his mom's boyfriend, teaches. While there, he meets Rachel Elizabeth Dare, a clear-sighted mortal whom he met previously at the Hoover Dam in The Titan's Curse. During the orientation, Rachel suddenly runs away to the gym. Percy follows her, and she tells him that something is wrong with the two presenting cheerleaders, Tammi and Kelli.
The people in question enter the gym where they reveal themselves to be Empousai. Percy slays Tammi, but Kelli disappears in a burst of fire. Unfortunately, Paul Blofis and some other mortals see the incident forcing Percy and Rachel to escape through a broken window. They both run outside to where Annabeth is waiting. Rachel leaves Percy, telling him to explain everything when he has time. Then, Percy, along with Annabeth make their way to camp.
After reaching camp, Annabeth decides to go talk to Clarisse La Rue about something secret, leaving Percy to wander the camp by himself. He stops by the arena and sees a massive hellhound, Mrs. O'Leary. He tries to kill her, but is soon stopped by Quintus, the new sword-master, who reveals that Mrs. O'Leary is his pet. Chiron interrupts their conversation and takes Percy to Grover Underwood. He leads them to a glade where the Council of Cloven Elders is being held and drops him next to Annabeth, Clarisse and a crying nymph, Juniper, who turns out to be Grover's girlfriend.
The council decides that Grover has only one week to find Pan, the lost God of the Wild. Otherwise, his searcher's license will be forfeited. The meeting concludes, and Percy rushes over to clean up his cabin for the cabin inspection. As soon as he reached the Poseidon cabin, he sees his half-brother, Tyson, cleaning up. Tyson hugs him and shows him the repaired shield that latter broke last winter during the fight with the manticore.
Later that night, Percy has trouble sleeping. He realizes that the room is glowing with a faint blue light coming from the saltwater fountain his father had given him last winter. Surrounding it is a rainbow colored light, clearly an Iris Message. He deposits one drachma into the mist, and it shimmers until the figure of Nico di Angelo becomes clear. Nico is conversing with a ghost, asking if there is a way to bring Bianca di Angelo back to life. The ghost answers that it is possible, but only if an exchange happens — a soul for a soul. The vision vanishes before Percy has time to put in another drachma. In his mind, he has a chilling thought that Nico would come looking for him.
The next morning, in a camp game designed by Quintus, Annabeth and Percy are attacked by three giant scorpions. They try to find a place to hide, and squeeze between two boulders. They note that it must be the entrance to a tunnel. When they emerge from the entrance, it is revealed that they have actually discovered an entrance to the Labyrinth, a magical underground maze, under Zeus' Fist within the heart of the camp. Annabeth explains that this is the center of the secret mission Clarisse had undergone during The Titan's Curse — finding an entrance to the Labyrinth. She also explains that Luke Castellan might be planning to use it as an invasion route.
Into the Labyrinth
Annabeth leads a quest with Percy, Grover and Tyson to find Daedalus, the maze's creator. As soon as the group step into the maze, it confuses them, shifting its walls, narrowing its passageways, and closing off exits and entrances. They make it into a Roman-styled room where they find the minor god Janus. He offers Annabeth a key to one of the doors behind him. He forces her to make her choice when they are saved by the Queen of Olympus, Hera. She tells them that she has only delayed Annabeth's choice, and adds that the real reason for her visit was to offer them a wish. Annabeth wishes for a way to navigate the Labyrinth. Hera answers that she wishes for something she has already been given before vanishing.
They leave the room and end up inside Alcatraz, where they manage to rescue an ancient Hundred-Handed One, Briares, from Kampê. The group tries to convince Briares to join them, but the Hundred-Handed One has been so disheartened by the many years of imprisonment that he refuses. The group can do nothing but leave him as they move deeper within the maze.
The Triple G Ranch
They four meet Nico di Angelo at the Triple G Ranch. Percy makes a deal with Geryon to let Percy and his friends (including Nico) go if Percy cleans the stables of the man-eating horses. Percy returns successful, only to find all his friends bound and gagged. Geryon reminds Percy that he didn't swear upon the River Styx, therefore the deal is void. Percy defeats Geryon by shooting an arrow — guided by Hera — sideways through his body, and hitting his three hearts.
Nico refuses to leave with them, and they summon the ghost of Bianca di Angelo, where it is revealed that she had been sending Percy Iris Messages of Nico's plans. Bianca asks Nico to forgive Percy because her death was not his fault. She gives one final word of warning about the Fatal flaw of the children of Hades (holding grudges) before disappearing. Nico still refuses to leave with Percy and his friends, and Eurytion offers to let him stay for a while.
Eurytion also offers to help them find Hephaestus, who will help them find the way to Daedalus' workshop, by giving them a spider automaton which will lead them to the god of the forges. Once back in the Labyrinth, the foursome match wits with a Sphinx. They then meet Hephaestus, who tells them that he will divulge everything they would want to know about Daedalus only if they would find out who is invading his forges in Mount St. Helens and why. The four start to travel towards forges when Grover senses the presence of Pan.
The four split up. Percy continues the quest with Annabeth while Tyson accompanies Grover. Percy and Annabeth discover who the creatures using Hephaestus' forges are. As they scout the area, Percy is spotted by the telekhines and he is forced to fight them off. He tells Annabeth to get out of there and report back to Hephaestus. To Percy's surprise, Annabeth kisses him because she believes that Percy may die. Outnumbered, Percy summons water from within himself to defeat the monsters, but the resulting explosion sends him shooting into the air as he loses consciousness.
When Percy comes to, he finds himself on the phantom island called Ogygia. Percy meets its resident, a girl named Calypso, who is a daughter of Atlas, and a Titan. He feels an immediate attraction to her, and she, in turn, falls in love with him and offers him a choice — to stay with her and become immortal or to leave to help his friends. She gives Percy time to consider this. Hephaestus then visits them and privately explains to Percy what truly happened in Mount St. Helens.
He mentions that the energy Percy had unleashed had actually resulted in an earthquake that might have awakened Typhon, and Percy's resolve to return to the world falters. Hephaestus however, gives Percy a clear hint about how to navigate the maze, and he disappears into a pillar of fire. Percy makes his decision and decides to tell Calypso his choice at daybreak. His decision to return does not surprise Calypso. Before leaving, she gives him a sprig of moonlace to plant in Manhattan for her. She sends him on his way back to camp by giving him a magical raft to sail on, and as he travels the sea, he cannot help but think that she would always be his biggest 'what-if'.
Percy returns to the camp only to find it empty. He approaches the amphitheater where it becomes apparent that his burial shroud is being burned and everyone is present. He sees that Annabeth has made it back and makes his appearance. Though Annabeth makes a scene, the whole camp seems to be relieved that he is alive. Percy tells Chiron and Annabeth his plan after he figures out the hint that Hephaestus gave him, and soon, the two campers head into the mortal world to look for the one person they know that could guide them in the Labyrinth: Rachel Elizabeth Dare.
The trio go back to the Labyrinth and go look for both Daedalus' workshop and for Grover and Tyson. Rachel reveals how she can see the correct path as a faint brightness on the floor. They are suddenly captured by Luke's forces and are led to the arena of Antaeus, a son of both Poseidon and Gaia, where Percy sees Luke and the rest of his forces . It becomes clear that Luke knows the arena is part of the path, and in order to pass, he provides Antaeus entertainment in the form of gladiatorial fights.
Because they share the same heritage through their father, Antaeus takes a special interest in Percy. The latter is given a turn to fight in the arena against another half-blood, Ethan Nakamura. Though Percy clearly has the upper hand, he refuses to kill Ethan. This causes Antaeus in his rage to fight Percy himself. Through trickery and wits, Percy manages to slay Antaeus. Luke orders his forces to slay them, however Percy uses the Stygian ice whistle Quintus had given him earlier and summons Mrs. O'Leary. The three, along with Ethan, escape but as soon as they are far from the arena Ethan leaves them.
The group soon reach Daedalus' workshop where they find Quintus, who reveals himself to be Daedalus. They converse with him only to find out that though he pities them and the camp, he has already made up his mind to help Luke as he had given the latter the magical item that could help the user navigate the maze — Ariadne's string.
Their conversation is cut short when Kelli the empousa, Minos — Daedalus' greatest enemy and the ghost pretending to help Nico — and some of the other enemy forces arrive with Nico in tow. Daedalus, the trio, and Nico battle the monsters. Mrs. O'Leary appears and helps them. Daedalus tells the four to escape, and they flee to the mortal world using his improved metal wings. Rachel is able to quickly get them a ride back into the Labyrinth.
They come across a tunnel which Percy figures out to be the entrance to the Titans palace. He enters alone, fearing for the safety of the others. Inside, he finds and opens a golden sarcophagus and is shocked to see that it is not Kronos, but it is Luke who is inside. Percy guesses that Kronos must have fused with Luke. He stays long enough to see Ethan enter and pledge allegiance to Kronos while some telekhines holding Kronos's scythe watch on. Kronos awakens and Percy tries to run from him, but Kronos stops time. Suddenly, Rachel throws a hairbrush at the Titan's face. Luke yells in pain, but Kronos regains control as Nico summons a wall of black stone, giving the four of them time to escape.
After their flight, Percy and Annabeth argue about Luke. Percy tells her that Luke has turned completely evil, but Annabeth refuses to believe this as she had seen that it was Luke who cried out when Rachel hit him with the hairbrush. Percy goes to talk to Rachel but is stunned when he sees Grover's cap lying on the ground. The cap is lying near the entrance to a tunnel, and the four push farther in. There, they find Tyson and an unconscious Grover. They manage to wake Grover, and together, the six finally enter Pan's last resting place, Carlsbad Caverns under New Mexico.
The god asks Grover to spread the word that Pan truly is dead, as his domain is much too damaged to be saved. Though Grover initially refuses, he eventually gives in. Pan addresses each of them individually with the exception of Nico. Pan finally dissolves, and a small curl of white mist enters the six, with Grover getting a bit more than the others. They make it out of the Labyrinth and Rachel tells Percy that her father is a very rich land developer which explains why she was able to quickly get them a ride back into the Labyrinth, and why she felt guilty about Pan's passing. Percy reassures her that it is not her fault. Soon, the three campers and Nico fly on pegasi back to camp.
The Battle of the Labyrinth
The four make it back in time to see the camp making preparations for war. Percy and Chiron are able to talk for a while before Kronos' army explodes from the Labyrinth. The campers, along with the satyrs, nymphs, and Chiron, do their best to hold the enemy forces off. Daedalus, Mrs.O'Leary, and Briares appear, and it seems that the camp may be saved, but Kampê suddenly bursts from the Labyrinth.
The odds are stacked against the camp when Grover unleashes panic, a gift from Pan, and the enemy forces scramble back to the Labyrinth. The demigods know that monsters will soon come back, and they start to regroup. Daedalus makes his choice to end his life, and therefore the Labyrinth, in order for the camp to be saved. Before he dies, he gives Annabeth a sleek silver laptop which contains all the ideas and notes that never had the chance to continue. Nico releases him, the Labyrinth is destroyed, and the camp is saved.
Later after dinner, Percy catches Nico just as the latter is about to leave. Nico apologizes for being such a brat to Percy, and Percy forgives him. Percy offers Nico a place in camp, but Nico refuses, saying that he could not be accepted in any place but with the dead. Percy lets him leave as he knows that Nico must find his own path.
Towards the end of the summer, Percy gets Annabeth to reveal the rest of her prophecy. Hera suddenly appears, and they both offend her by remarking that though she is the goddess of family, she only cares about perfect families. Hera replies that she will remember this insult, and disappears.
Percy goes back home, to celebrate his fifteenth birthday with his mom, Paul and Tyson. Poseidon arrives for Percy's birthday, and Percy explains everything to him. Poseidon tells Percy he is his favorite son and gives him a sand dollar before leaving. Nico suddenly appears, claiming that he has found a way to beat Kronos. Percy notes how wistfully Nico looks at the birthday food and invites him inside for both food and a talk.
You shall delve in the darkness of 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,
And lose a love to worse than death.
Unraveling the Prophecy
- Annabeth and her group go into the Labyrinth.
- Nico raises the dead, Ethan Nakamura joins Kronos after Percy saves his life, and Grover succeeds in finding Pan. (the dead, the traitor, and the lost one respectively).
- Nico calls himself the Ghost King during the battle in Daedalus' workshop, and he chooses to save Percy and Annabeth's lives.
- Daedalus' makes a decision on whose side to be on.
- Daedalus is willing to die for the Labyrinth's destruction (both being connected to each other).
- Luke gives his body as a host for Kronos.
- I Battle the Cheerleading Squad
- The Underworld Sends Me a Prank Call
- We Play Tag with Scorpions
- Annabeth Breaks the Rules
- Nico Buys Happy Meals for the Dead
- We Meet the God with Two Faces
- Tyson Leads a Jailbreak
- We Visit the Demon Dude Ranch
- I Scoop Poop
- We Play the Game Show of Death
- I Set Myself on Fire
- I Take a Permanent Vacation
- We Hire a New Guide
- My Brother Duels Me to the Death
- We Steal Some Slightly Used Wings
- I Open a Coffin
- The Lost God Speaks
- Grover Causes a Stampede
- The Council Gets Cloven
- My Birthday Party Takes a Dark Turn
- Percy Jackson - Main protagonist (son of Poseidon), helps Annabeth on her quest in the labyrinth. Percy also receives Mrs O'Leary, the hellhound at end of the book.
- Annabeth Chase - Daughter of Athena. Annabeth receives the quest from the Oracle and becomes the owner of all Daedalus inventions and one of his silver laptops at the end of the book.
- Rachel Elizabeth Dare - A mortal that can see through the Mist. She is also Percy's friend.
- Grover Underwood - A Satyr, and also Percy's best friend. Hates underground places. Becomes a Lord of Wild and a Chosen One of Pan. Grover also receives the cry of Pan after he dies which he uses to scare off Luke and his army.
- Juniper - Tree nymph. Also, Grover's girlfriend.
- Tyson - A friendly Cyclops who is a half brother to Percy.
- Daedalus - Son of Athena, inventor, and creator of the Labyrinth. In the end he is revealed to be Quintus and committed suicide to stop Luke and his army in the Labyrinth because the Labyrinth is tied to his life force.
- Nico di Angelo - Son of Hades and brother of Bianca di Angelo. In the last book he blamed Percy for his sister's death but forgives Percy while in the Labyrinth.
- Luke Castellan - Son of Hermes. Becomes the host of Kronos at the end of the book.
- Kronos - Rises in the end of the book, possessing Luke.
- Briares - the only remaining Hekatonkheires.
- Kampe - the ancient jailer of the elder Cyclopes.
- Empousai (Kelli and Tammi)
- Sally Jackson
- Paul Blofis
- Chris Rodriguez
- Clarisse La Rue
- Charles Beckendorf
- Silena Beauregard
- Connor Stoll
- Travis Stoll
- Lee Fletcher
- Tammi - Stabbed by Percy.
- Geryon - Killed by Percy in a duel using a bow and arrow.
- Antaeus - Stabbed by Percy when he wasn't touching the ground.
- Pan - Faded because of the severe damage to his territory.
- Kelli - Stabbed by Annabeth.
- Lee Fletcher - Son of Apollo, killed by a giant's club.
- Castor - Son of Dionysus/ Mr. D, killed by an enemy half-blood.
- Daedalus - He had Nico 'release' his spirit. His death means the destruction of the Labyrinth.
- When Percy returns to Camp Half-Blood from Ogygia, he sees the camp in the middle of a funeral for him. This could be a reference to the scene in Mark Twain’s The Adventures of Tom Sawyer where Tom Sawyer, Huckleberry Finn and Joe Harper return to town to find everything at their funeral.