It follows the adventures of three companions as they journey outside the magical land of Deltora to rescue the many prisoners held captive by the evil Shadow Lord.
Although he has defeated the enemy, Deltora is rotting away - the Shadow Lord had taken thousands of Deltorans as slaves back to the Shadowlands.
Lief and his friends must re-unite three pieces of the magical Pirran Pipe - the only thing the Shadow Lord fears - to save his people.
Meanwhile, the Deltoran Annals (a history of Deltora) are brought back by the chief librarian Josef when he returns from hiding and Lief learns of the Pirran Pipe, the only thing the Shadow Lord fears.
Lief and Barda follow her and, after escaping capture by the Granous (and Jinks fleeing back to Del) find a secret under-world.
The Plumes come to trust them and free the four Deltorans so they can attempt to defeat the Fear (a giant squid will flood the island if not provided with sacrifices).
Swinging on ropes to get past the Arach and into the dome, they find that only one person, the old Piper Auris, has remained behind to maintain the illusion.
Meanwhile, in Del, Jinks tries to steal the royal jewels and flee the city, but accidentally eats poisoned food intended for Marilen.
It is discovered that it was poisoned by Amarantz, Josef's friend from the resistance who was working as a cook, and that the Shadow Lord is using worms implanted in the brains of former captives to control their minds, explaining the recent attempts on Lief's life.
Lief, Barda and Jasmine sneak into the Arena just as the Shadow Lord is about to wipe the slaves' memories with worms that will control their minds.
The Piper's son, Emlis, starts playing the Pirran Pipe and Lief, Barda, Jasmine, Claw, Emlis and all of the slaves are teleported back to the secret sea by the Keras, as the Pirran tribes can transport people between the surface and the caves, and heard the Pipe's music.