Lucy and Edmund Pevensie return to Narnia with their cousin Eustace where they meet up with Prince Caspian for a trip across the sea aboard the royal ship The Dawn Treader. Along the way they encounter dragons, dwarves, merfolk, and a band of lost warriors before reaching the edge of the world.

During World War II, the Pevensie children, Peter Pevensie, Susan Pevensie, Edmund Pevensie and Lucy Pevensie, are evacuated from a London suburb to Professor Digory Kirke's country home. Mrs Macready, the strict housekeeper, explains he is unaccustomed to hosting children.

In Narnia (world), almost 1300 years after the Pevensie siblings left. Caspian X, a Telmarine prince, is awoken by his mentor Doctor Cornelius, who informs him that his aunt has just given birth to a son and that his life is now in grave danger. Cornelius gives him Susan Pevensie ancient magical horn and instructs him to use it if he is in dire need of help. Knowing that his Uncle Miraz would kill him in order to be king, Caspian flees. Chased by several Telmarine soldiers, Caspian falls off his horse and encounters two Narnian dwarfs and a talking badger in the woods. One of the dwarfs, Trumpkin, is captured by the soldiers after sacrificing himself to save Caspian, while the other dwarf, Nikabrik, and the badger Trufflehunter, save Caspian. Not knowing that they are trying to save him, Caspian blows the magical horn, trying to summon help.

1956, France. A priest is murdered, an evil is spreading, and Sister Irene once again comes face to face with the malevolent force of Valak, the demon nun.