En stresset læge forlader storbyen og slår sig ned på landet i et malerisk idyl. Men samtidig er der en anden nyankommen til byen, et stort, låddent kryb med otte ben, som slår sig ned i familiens lade, og kort tid herefter bliver den lille by rystet af en række dødsfald.

Den døende mogul, Murdoch, hyrer en doktor til at finde en frisk forsyning blodorkideer og eksperimentere med den livs tilbage bringende nektar på en baby slange. I løbet af natten vokser slange-ungen sig til et kæmpemonster med appetit nok til at spise den gode doktor i en mundfuld, før den bugter sig væk og går amok. Den smukke herpetolog, Amanda, er opsat på at tilintetgøre det onde bæst, som hun hjalp med at skabe, og leder et team af unge videnskabsfolk mod en ubarmhjertig hær af Murdoch's bevæbnede banditter, der prøver at få fat i den eftertragede orkidé før slangen hugger begge hold ned. Den blodtørstige unge synes uovervindelig, som den glider mellem eksplosioner og pistolskud, blot for at genopstå og æde alt hvad den finder sin vej.

Africa in the sixties. The Nile perch, a ravenous predator, is introduced into Lake Victoria as a scientific experiment, causing the extinction of many native species. Its meat is exported everywhere in exchange for weapons, creating a globalized evil alliance on the lake shores. An infernal nightmare in the real world that wipes out Darwin's Theory of Evolution.

In 1890, one man had the idea to collect every bird ever mentioned in Shakespeare and release them into Central Park. The only bird to survive in the New World was the European starling, which became one of the most common birds in North America. Its introduction is now widely considered a major environmental disaster.

In 1940 twenty Canadian Beavers were brought to 'Tierra del Fuego' island in southern Patagonia for commercial fur production. However, beavers having no natural predators, quickly spread throughout the island, causing massive destruction of trees threatening the entire Patagonian forests rivers and species. Why wildlife conservationist are convinced that 150.000 beavers must be killed? Why some of the most recognized specialist are convinced that an eradication is not possible? Meanwhile truism is capitalizing on the situation: a man dressed as a beaver passes out flyers promoting a famous sky resort: 'Cerro Castor' - Beaver Hill. Hunters claim for subsidies, scientists are researching, rangers do what they can and restaurants tray to offer beaver meat to tourist.

After decades of hurricanes and oil spills, Louisiana faces a new threat - hordes of monstrous 20 pound swamp rats. Known as "nutria", these invasive South American rodents breed faster than bounty hunters can "control" them. With their orange teeth and voracious appetite they are eating up the coastal wetlands that protects Thomas and his town of Delacroix Island from hurricanes, but the people who have lived here for generations will not give up without a fight.

Cats are cuddly felines and lovely pets, but also highly evolved predators that hunt huge amounts of small mammals, birds and reptiles; perfect killing machines that threaten delicate ecosystems around the world.