Exposition

Edmund and Lucy Pevensie were spending the holidays at their cousin, Eustace Clarence's home. In Lucy's room they looked at the picture on the wall above Lucy's bed. It was of a Narnian ship, the 'Dawn Treader'. The ship comes to life where "down went the prow of the ship into the ware and up went a great shock of spray". Soon they were drowning in the water beside the 'Dawn Treader'. On board the ship, they found the Prince of Narnia, Caspian. (Chapter 1: The Picture in the Bedroom, pages 4 - 12)

Prince Caspian explained to them about his quest. "A longtime ago as a child my usurping uncle Miraz got rid of seven friends of my father's (who might have taken my part) by sending them off to explore the unknown Eastern Seas beyond the Lone Islands. On my coronation day, with Aslan's approval, I swore an oath that, if once I had established peace in Narnia, I would sail east myself for a year and a day to find my father's friends or to learn of their deaths, and avenge them if I could.
(Chapter 2: On Board the Dawn Treader, pages 20 - 21)