Edmund (Skandar Keynes) and Lucy (Georgie Henley) return to Narnia with their cousin, Eustace (Will Poulter), by onboard a ship called Dawn Treader where they meet Caspian X (Ben Barnes) Now is the King of Narnia. Peter and Susan do not return because they have learned all they need in Narnia. Apparently in the third year of his reign, King Caspian to travel by ship The Down Treader to find the seventh missing people Lords. The Lords are the friends of King Caspian's father who was ousted by King Miraz. Edmund and Lucy were so happy could return to Narnia, but not with Eustace that is not exited and being annoying.
King Caspian was accompanied by his captain, Lord Drinian, second officer Rinche and the crews where one of them named Rynelf and the brave mouse, Reephicheep on the way to reach the Sea of East.
The Down Treader goes around the Narnia world. They began their journey and they meet many thing in their Journey. Edmund, Lucy and Eutace have great experience along the journey, one of them is when Eustace turn into a Dragon. In form of a Dragon , Eustace became aware of a previous naughty behaviour. He changed for the better by helping the group by his ability as a Dragon.
Lucy, Edmund, and Eustace in the shallow place and found a Lamb that offered a breakfast of a grilled fish. Lamb was later turn into Aslan who tells Lucy and Edmund that they will never return to Narnia again. They were asked to learn about Aslan who has another name in their world. At the end is told about Eustace who has turned into good boy and King Caspian who eventually married the daughter of Ramandu.