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.