Thunk goes missing after the Thunder Sisters dismiss his help during a battle. The Thunder Sisters, and Grug, Phil, and Guy's newly formed "Thunder Sifters" search on and off the farm for Thunk.

Phil enlists the Croods to help him retrieve a rare fruit before some wild animals can. But when Grug doesn't trust Phil's methods of getting it back to the farm, the Croods and Bettermans compete with each other more than with they did with the animals.