One day, Lucy and Edmund are forced to go visit their Uncle Harold, Aunt Alberta, and cousin Eustace, whom they particularly dislike because of his selfishness and unpleasant attitude. On that visit, a painting of a ship on a wall suddenly looks like it’s coming to life, and during a struggle, the three children all fall right into the painting—and into the ocean of the world of Narnia.
Lucy and Edmund are glad to be back in Narnia, where their old friend Caspian rescues them from the water in his ship, the Dawn Treader. Eustace, however, constantly complains about the situation and just wants to go home. Caspian is heading east on the Dawn Treader toward the World’s End, fulfilling a promise he made when he became king to sail east and find the seven lost lords of Narnia. He hopes he might also see Aslan’s country, a mysterious land that seems to be somewhere in the east.
The three children meet the other crew members of the Dawn Treader, which include Drinian (the captain) and Reepicheep, a brave talking mouse who is on the journey because when he was younger, he received a prophecy that he must sail east. Eustace gets in trouble by picking fights with crew members and refusing to help out.
Over the course of its journey east, the Dawn Treader stops at many unusual islands, where Caspian and the children go on adventures. At the Lone Islands, ruled by the corrupt Governor Gumpas, the children nearly get sold into slavery, but Caspian uses his authority as king of Narnia to depose Gumpas and abolish slavery.
On Dragon Island, Eustace finally decides he’s had enough of work, and so he goes off on his own, getting lost in the island’s foggy mountains. Lonely, he wants to find his companions, but instead runs into the corpse of a dragon near a horde that contains a golden armband. Eustace puts on the armband and accidentally gets turned into a dragon himself. It’s only with Aslan’s help that Eustace manages to shed his scaly dragon skin and become a human again. Eustace’s experiences as a dragon teach him to be less selfish, although he still keeps some of his old flaws.
The Dawn Treader runs across many other strange sights, including a sea serpent and an island with a special pool that turns anything that touches it to gold. Eventually, they reach the island of a Magician, which is full of a strange group of invisible creatures. Lucy agrees to help the creatures by finding the Magician’s book of spells. Although the magic book tempts her with promises that she will become beautiful and popular, she resists temptation with Aslan’s help and manages to make the island’s residents visible again.
The Dawn Treader continues its voyage, passing a mysterious place known only as Dark Island, which falsely promises to fulfill men’s dreams. Everyone except Reepicheep is tempted by the island, but they manage to pass it safely. The crew comes to the island of a retired star named Ramandu, where they see three of the Narnian Lords sleeping by a table. Ramandu tells them that the only way to wake the three Lords is to go to the very end of the world, leave a crew member there, and then come back.
The Dawn Treader leaves the island and keeps sailing east. The water near the end of the world is very clear, and beautiful sea people have made their own civilization underwater. At last, the water is too shallow for the Dawn Treader to continue. Caspian is tempted to keep going toward the World’s End, but his crewmates convince him that it’s his duty to act as king and to fulfill his promise to wake the Lords on Ramandu’s island. And so, only Reepicheep, Edmund, Lucy, and Eustace continue east, taking a smaller boat until it’s so shallow they have to walk. Reepicheep keeps going east and is never seen in Narnia again, while the three children eventually turn off to go south.
The three children run into a talking lamb that turns out to actually be Aslan. Aslan tells Edmund and Lucy that they will never go back to Narnia again because they have no need to do so. Although they’re sad, Aslan promises that the children will all see him again someday and that he also exists in their world, by another name.
The children finally make it back to their own world, where everyone appreciates how much more mature Eustace is, except for Alberta.
