Luckily for Dave and his son Finny, two Nestrians, an Ark has been built to save all animals. But it turns out, Nestrians aren't allowed. Sneaking on board with the involuntary help of Hazel and her daughter Leah, two Grymps, they think they're safe. Until the kids fall off the Ark.

Now Finny and Leah struggle to survive the flood and hungry predators and try to reach the top of a mountain, while their parents Dave and Hazel must put aside their differences, turn the Ark around and save them.

It's not going to be smooth sailing.