Littlefoot, a young Apatosaurus living in the verdant Great Valley, is eagerly awaiting the arrival of his father Bron, who returns to the valley with his herd once a year. However, he soon learns from a Nothronychus member of his dad’s troupe named Wild Arms that his father became stranded in the wilderness when the “fire mountain” erupted, leaving the rest of the herd to go on without him. Embarking on a journey with his friends - Cera, Ducky, Petrie, and Spike - Littlefoot enters the Mysterious Beyond to try and rescue him on their own.