Boots falls through an open air duct in the laundry room and Gregor dives in after her, landing in the Underland.

Giant cockroaches carry Gregor and Boots through tunnels to the underground human city of Regalia.

Gregor meets Luxa, the future queen of Regalia, and her advisor Vikus for the first time in the arena.

Gregor escapes alone on the Underland river at night but is cornered by two enormous rats named Fangor and Shed.

Gregor reads the Prophecy of Gray and learns a warrior Overlander must lead a quest to save his missing father.

A dying woman on a bat crashes into the Council chamber, warning that King Gorger has launched his full army.

The quest departs Regalia with Gregor, Boots, Luxa, Henry, Temp, Tick, and their bat companions.

Hundreds of cockroaches perform the sacred Ring Dance around Boots, honoring her as a chosen figure.

Gregor saves Luxa from Spider Queen Wevox by shaking a root beer can and spraying it into the spider's eyes.

Tick sacrifices her life by flying directly into the lead rat so Boots and Temp can cross the bridge safely.

Ripred reveals Gregor's father is only an hour away and guides the companions toward his prison pit.

Henry reveals he has been King Gorger's double agent and whistles for the encircling rat army.

Gregor leaps over King Gorger and sprints into the canyon, drawing the entire rat army down after him.

Ares chooses to rescue Gregor instead of Henry; Henry and the rats crash at the canyon bottom.

Gregor's family emerges from the Underland in Central Park and takes a cab home to their mother.

Gregor falls into the Underland while chasing his toddler sister Boots through a laundry room vent, arriving in Regalia, the underground human kingdom ruled by young Luxa. He learns the Prophecy of Gray calls for an Overlander warrior to lead a quest and rescue his long-missing father, and after King Gorger's army is announced, the full party departs. The group battles rats and spiders across dangerous caverns, losing their cockroach companion Tick in a selfless sacrifice before finally locating Gregor's father. Henry's betrayal triggers a desperate climax in which Gregor leaps into a canyon to draw the rat army away from his companions. Ares the bat chooses to save Gregor over his bonded rider Henry, and the two crash into the canyon below. Gregor's family exits the Underland in Central Park and returns home to reunite with their mother.

The Overlander's journey from New York to the Underland and back.

Gregor does laundry with Boots in the apartment building while reflecting on his father's years-long disappearance.

The cockroaches debate whether to bring Gregor and Boots to the rats or the humans.

Vikus tells Gregor that returning to the Overland requires much giving and cannot happen quickly.

Vikus tells the history of Regalia's founder, Bartholomew of Sandwich, who led followers underground in the 1600s.

Gregor discovers the palace water system and decides to use it as his secret escape route.

Gregor kills the rat Fangor by throwing his torch directly into the rat's face during the rescue battle.

Luxa arrives at the river beach battle and kills Shed while flying completely upside down on her bat Aurora.

The Council of Regalia votes ten to two that Gregor is the prophesied warrior of the Prophecy of Gray.

Nerissa hands Gregor a written copy of the Prophecy of Gray, having sensed he silently wanted it.

The companions are taken prisoner by Spider Queen Wevox after Gregor runs headlong into her enormous web.

Gregor uses Boots's screaming cookie tantrum as a distraction so Luxa can perform the Coiler and shred the web.

Solovet, Vikus, and Mareth announce they must return to Regalia for the war, leaving the questers alone.

Ripred leads the questers through a foul, narrow tunnel for hours to mask their scent from enemy rats.

Gregor's father uses a magnetized needle and a lodestone to build a compass pointing north toward Regalia.

Gregor publicly speaks the bonding vow to Ares in the arena, preventing the bat's banishment from Regalia.

Before the adventure begins, Gregor is a homesick boy doing laundry who has spent years waiting for his missing father, and his first escape attempt ends in disaster when giant rats corner him on the riverbank. The ensuing battle reveals the Underlanders as his protectors, and back in Regalia the Council votes to officially recognize him as the prophesied warrior. The quest takes the group through the spider realm, where they become prisoners before escaping through clever use of Boots's tantrum and Luxa's daring Coiler maneuver. Solovet and Vikus then announce they must return to fight the war at home, and the rogue rat Ripred guides the remaining questers deeper into enemy territory through a foul hidden tunnel. Gregor's father is the one who finally engineers their path home by building a makeshift compass from a lodestone. The story closes with Gregor speaking the sacred bonding vow to Ares in front of the assembled Underland court, saving the bat from banishment.

Behind-the-scenes decisions and battles that shaped the quest.

Vikus reveals there is only one gateway to the Underland from New York City, making Gregor's arrival rare and anticipated.

Luxa strikes Gregor across the face; Vikus then reveals her parents were both killed by rats.

Vikus produces a braided leather keychain, and Gregor recognizes it as one he made for his father.

Vikus reveals that Gregor's father is believed to be alive and held prisoner by King Gorger's rats.

Vikus tells Gregor directly that he believes Gregor himself is the warrior from the Prophecy of Gray.

Gregor refuses to join the quest unless Boots accompanies him, forcing the entire Council to accept her.

Vikus formally invites the cockroaches Temp and Tick to eat alongside the questers, declaring all members of the prophecy equal.

Gox the orange spider arrives carrying dying Treflex, revealing King Gorger's rats have attacked and betrayed the spiders.

Vikus introduces Ripred as the group's rat guide and reveals for the first time that he is Luxa's grandfather.

Henry attempts to kill sleeping Ripred with his sword; Gregor physically places himself between them to stop the fight.

Luxa confesses to Gregor she has not cried once since her parents died; Gregor silently forgives her everything.

Luxa refuses Henry's offer to defect to King Gorger, choosing loyalty to Regalia over her own survival.

Gregor realizes the prophecy's final line refers to him as the warrior and leaps directly over King Gorger.

Gregor sews up Aurora's torn wing and realizes, with Luxa in shock, that he must now lead everyone home.

Gregor refuses Bartholomew of Sandwich's sword and tells Vikus he wants to be a diplomat, not a warrior.

Gregor's world shifts when Vikus produces a braided leather keychain he recognizes as his father's, confirming his father reached the Underland and may still be alive in the rats' lair. Committing fully to the quest, Gregor refuses to leave Boots behind and declares himself the warrior to the Bat Queen to secure her bats' cooperation. Along the way, small acts of equality reshape the group: cockroaches are formally invited to dine as equals, and the arrival of betrayed spiders reveals how far King Gorger's treachery reaches. Gregor steps between Henry and Ripred to prevent a killing, and a quiet moment with Luxa in which she confesses she has not cried since her parents' deaths transforms them from adversaries into true allies. Henry's betrayal and Ares's heroic choice in the canyon force Gregor into unexpected command of the battered survivors. Back in Regalia, Gregor refuses the legendary sword of Bartholomew of Sandwich, declaring that he wants to build peace rather than wield weapons.