Original: The Pevensie children help Aslan, a talking lion, save Narnia from the evil White Witch, who has reigned over the land of Narnia for a century of perpetual winter.
Simplified: But at this time, Narnia is under the spell of a witch. The children then fulfill an old prophecy as they help Aslan (a lion) save Narnia from the evil White Witch, who had ruled over the kingdom for a hundred years.