The story of a dinosaur named Arlo. The dinosaur has a family: a mother named Ida, a father named Henry, and a brother and sister named Libby and Buck. The family is engaged in the household. And while his brother and sister are doing well, Arlo doubts himself and does not know what to do.

To keep his son busy, Henry sends Arlo to set traps in the area. A small cave boy falls into one of Arlo's traps. Arlo is too kind to kill the boy, and he lets him go. However, Arlo's father cannot make such a mistake. Therefore, Henry and his son go in search of the cave boy, but they themselves fall into a trap and Henry dies saving his son. Now Arlo blames the boy for his father's death. And continues to search for the boy in order to take revenge on him. But when Arlo finds the cave boy, they fall into the river together and are carried away by the current.