Back in Far Far Away, Shrek and Fiona share news of their marriage. But a sinister plan involving Prince Charming threatens their "happily ever after."

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.

Life in the swamp seems better than ever for Shrek and Fiona, until King Harold suddenly falls ill and the adorable ogre must find an heir.