As the son of a Viking leader on the cusp of manhood, shy Hiccup Horrendous Haddock III faces a rite of passage: he must kill a dragon to prove his warrior mettle. But after downing a feared dragon, he realizes that he no longer wants to destroy it, and instead befriends the beast – which he names Toothless – much to the chagrin of his warrior father.

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.