Having magically traveled to the land of Narnia where they were treated as kings and queens and defeated the evil White Witch while helping return Aslan the Lion to power, the Pevensie siblings -- Peter (WILLIAM MOSELEY), Susan (ANNA POPPLEWELL), Edmund (SKANDAR KEYNES) and young Lucy (GEORGIE HENLEY) are now back in WWII era London.
Little do they know, however, that 1,300 years have passed since their departure and that human Telmarines have apparently hunted the Narnians into extinction. But that doesn't mean the conquerors are above killing their own kind, for once Queen Prunaprismia (ALICIA BORRACHERO) bears Lord Miraz (SERGIO CASTELLITTO) a son, the scheming ruler deems his nephew, Prince Caspian X (BEN BARNES), expendable.
Thankfully, his mentor, Doctor Cornelius (VINCENT GRASS), warns him of the pending treachery, thus allowing the young prince to escape into the nearby woods with General Glozelle (PIERFRANDESCO FAVINO) and his men in hot pursuit. There, Prince Caspian encounters Trumpkin the Red Dwarf (PETER DINKLAGE) and Nikabrik the Black Dwarf (WARWICK DAVIS) who aren't pleased to see a Telmarine in their midst.
Glozelle captures Trumpkin, but Caspian manages to get off a distress call before Nikabrik gets him. That summons the Pevensie kids who are magically transported back to Narnia where they're shocked to find nothing but ruins, although Lucy hasn't lost faith that Aslan (voice of LIAM NEESON) isn't far away.
Miraz, meanwhile, is using Trumpkin's presence to convince the other rulers, such as Lord Sopespian (DAMIAN ALCAZAR) that the Narnians are not only still around, but in great numbers and must be exterminated. Of course, he pushes that agenda because he knows Caspian is still in the Narnia woods and must be dealt with.
Caspian soon finds himself in the company of talking animals, such as Trufflehunter the Badger (voice of KEN STOTT) and Reepicheep the Mouse (voice of EDDIE IZZARD), along with mythological creatures including Asterius the Minotaur (SHANE RANGI), Glenstorm the Centaur (CORNELL S. JOHN), and others of their kind. Knowing the Telmarine world, the prince is chosen to lead the Narnians in battle against them, but is role is usurped by Peter and his siblings.
From that point on, and vastly outnumbered, they, Prince Caspian and the various Narnians do what they can and must to save themselves.