One year has passed in our world since the first adventure ended, but in Narnia, almost 1300 years have passed. The villainous King Miraz prevents the rightful heir, his young nephew, Prince Caspian, from ruling the land of Narnia. Caspian uses Susan's magic horn that was left in Narnia to summon the four Pevensies and a small army of Old Narnians to help him reclaim his rightful throne, and find Aslan. (wiki)