A bedtime story leads Littlefoot and his grandparents on a journey to a new land, where Littlefoot discovers someone who vanished before he was born: his father! Now Littlefoot must decide between two worlds. Will he leave to be with his friends in the Great Valley, or stay behind and start a new life with his father?

This fourth sequel in the series finds “leaf gobblers” eating all the vegetation in Great Valley, driving Littlefoot, the young brontosaurus, and the other dinosaur inhabitants out. Arguments break out among the adults during migration, and Littlefoot and his friends decide to take matters in their own hands by crossing the “big water” to an unknown island. There they meet an old friend from The Land Before Time II–Chomper, the T-rex, who has to protect the gang from his own, carnivorous parents. Plenty of drama in this one, and as the series has been wont to do from the beginning, it shows adults as sometimes being less than perfect.