Primatologist Davis Okoye, a man who is the head of an anti-poaching unit, finds out his beloved albino silverback gorilla friend George has been infected with a mysterious experiment that turns him into a giant, aggressive beast. To make matters worse, a grey wolf named Ralph and an American crocodile named Lizzie have been infected too. With the help of a discredited genetic engineer named Dr. Kate Caldwell, he must save George, stop Ralph and Lizzie from destroying most of America, and find out who mutated the animals.