In the adventurous third installment of C.S. Lewis' Narnia tales, the two younger Pevensie children return to Narnia with their unwilling cousin Eustace (should have been named "Useless") and travel with the now adult King Caspian on a high sea adventure. The story begins with the two younger Pevensie children, Lucy and Edmund, being sent into a sort of exile to their cousin's house for the summer. Eustace is a tiresome boy more interested in grain elevators and pictures of fat chinese children than in adventure. But when he catches his cousins looking at a picture of a "Narnian" ship and begins to tease them, he gets more than he bargains for when the picture becomes real and the three children find themselves adrift on a Narnian Sea. Rescued by the crew of the Dawn Treader, Lucy and Edmund are overjoyed to find that their friend King Caspian is on board and they enthusiastically join his search for seven missing lords who had left Narnia years earlier to explore the seas. As the children have many adventures exploring the uncharted islands they are captured by slave traders, overcome a so called evil magician, repel the attack of a sea monster and survive a terrible storm. By the end of the voyage, they have found all of the missing Lords and Eustace has had a new birth.
Like all the Narnia stories, this one also contains an allegorical message. In one of the strongest allegorical points in the series, Eustace is transformed into a dragon after sleeping a a dragon cave with greedy thoughts in his head. As a dragon, Eustace gets to see his shipmates in a new light. He has been a constant problem on board ship with his complaining and whining as well as his refusal to help with the work on board or give Caspian the obedience he deserves as king. Now as his shipmates first figure out Eustace's plight and try to help him, he has a change of heart. In a symbolic moment, Aslan, the Great Lion(who represents Christ in the series, appears to Eustace and brings him to a pool of water telling him to take off the dragon skin. Eustace proceeds to scratch off his skin several times but only finds another dragon skin underneath. Finally Aslan takes Eustace and using his sharp claws, removes the dragon skin completely so that Eustace is a boy again. This sharp picture portrays the Christian belief that the sinner cannot cast off sin by himself, but that only Christ can cleanse one from sin. Later in the story when the children and Reepicheep the Mouse set off to find Aslan's country they first encounter him in the shape of a lamb, also symbolic of Christ. When story ends, the younger Pevensie children are now told that they will not be able to return to Narnia but readers of the series will see Eustace again in the next adventure written by Lewis: The Silver Chair.