65 million years ago, an asteroid passed by the earth, and the dinosaurs that dominated the world escaped the catastrophe in a daze. Millions of years later, the intelligence of dinosaurs evolved. They learned to plant, raise livestock, build, and have their own language and family. In the plains at the foot of a mountain, the Brontosaurus family welcomed three babies with different personalities. The youngest, A Luo (voiced by Raymond Ochoa), was weak and timid, and the separation from his father cast an indelible shadow in his heart. After a series of events, he was thousands of miles away from his mother, brother, and sister. A Luo blamed all this on the primitive human child Diandian (voiced by Jack Bright). But Diandian seemed unmoved, and he took the initiative to get close to A Luo, as if he was a loyal and brave puppy. On the bumpy and dangerous road home, Arlo and Diandian travel together, and these two dinosaurs and humans who should not have met will establish a pure friendship that transcends race and time and space...