Five years have passed since Hiccup and Toothless united the dragons and Vikings of Berk. Now, they spend their time charting unmapped territories. During one of their adventures, the pair discover a secret cave that houses hundreds of wild dragons -- and a mysterious dragon rider who turns out to be Hiccup's mother, Valka. Hiccup and Toothless then find themselves at the center of a battle to protect Berk from a power-hungry warrior named Drago.

The prehistoric Croods family live in a particularly dangerous moment in time. Patriarch Grug, his mate Ugga, teenage daughter Eep, son Thunk, and feisty Gran gather food by day and huddle together in a cave at night. When a more evolved caveman named Guy arrives on the scene, Grug is distrustful, but it soon becomes apparent that Guy is correct about the impending destruction of their world.