Young Prince Caspian of Narnia wonders and dreams about the old days of Narnia when animals talked, and there were mythical creatures and four rulers in Cair Paravel. But his uncle and aunt don’t like to hear him thinking of such things, and plan to murder him and take his throne. Caspian’s tutor, Dr. Cornelius manages to save him, and not only teach him about the old ways, but bring him into the real Narnia and introduce him to the real Narnia. But Caspian’s plight is desperate, and he must use the legendary horn to call help from another world: Peter, Susan, Edmund, and Lucy. Then, Lucy and Edmund are sent back to Narnia, along with their cousin Eustace, to assist Caspian on a voyage. Along their journey the children battle dragons and sea serpents, and sail across a golden lake to reach the edge of the world.

Eustace is sent to a horrible school, and finds a friend in Jill Pole, who's also running from the bullies and looking for a place to hide. The two of them are magically transported from the garden shed into the magical world of Narnia, where they are entrusted with a task by Aslan: to rescue the king's stolen son, Prince Rillian. Together with Puddleglum the Marshwiggle, they must travel north across the mountains, dodge dragons and giants, and journey down into the earth itself to rescue Rillian from the Green Lady.