In the adventurous third installment of C.S. Lewis' Narnia tales, Lucy and Edmund Pevensie, the younger two of the four children, return to Narnia with their unwilling cousin Eustace Clarence Scrubb (who Lewis says almost deserved that name) and find themselves traveling with King Caspian, who is now an adult, on a high sea adventure. Lucy and Edmund were spending the summer at their cousin's house and having a rather miserable time of it. Eustace was not very kind to them, but when he catches the two staring at a painting of a Narnian-looking ship, he begins to tease them. In so doing, he gets quite the surprise when the picture comes to life 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. After a brief reunion, they 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 an awakening as to how his behavior has affected his life and those around him.
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 falling asleep in 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 even to give Caspian the obedience he deserves as king. 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 (while he is the dragon) 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 Silver Chair.
Quotes from The Voyage of the Dawn Treader by C.S. Lewis