Inside of Rocco's Pet Emporium, the animals are restless in their cages, sensing the oncoming storm. But none feel the anxiety as keenly as the rats, whose dying prophet Nezumi has given them a dire warning: Get out, before the Big Water comes. As the city trembles under the wrath of a violent storm, the rats of Rocco's Pet Emporium are faced with an insurmountable challenge: Escaping from the confines of their cage, the only world they have ever known, to seek shelter from the flood. Abandoned by the humans they once worshiped as gods, the rats must now face disaster on their own. But they are not alone. The Wild Ones, long kept subdued by the threat of humans, have emerged to take over their rightful territory. And they'll kill anyone who gets in their way.