Millionaire zoologist Eric Gorman, overcome with suspicions about his wife's fidelity, murders her suspected lover, Bob Taylor, by sewing his mouth shut and leaving him helpless in a jungle in Indochina. An Indochinese later reports to Gorman, who pretends to be shocked, that Taylor was found to have been eaten by tigers. Gorman returns to the United States with a menagerie of wild animals to be housed in the zoo. He commissions the zoo's laboratory doctor, Jack Woodford, and Jack's assistant and fiancée Jerry Evans, daughter of the head of the zoo, to find an antitoxin for the mamba, a deadly snake. Meanwhile, the newly-hired press agent Peter Yates, who is afraid of most of the animals in the zoo and has a reputation as a drinker, holds a fundraising dinner in the carnivore house. When Roger Hewitt suddenly dies at the dinner from a mamba bite, Jack discovers his laboratory mamba is missing. The zoo is temporarily closed due to the missing snake. When Gorman's wife Evelyn accuses him of killing Roger, with whom she was having an affair, he tries to attack her. She escapes into his office and finds a mechanical mamba head in his desk drawer, with poison in it. Realizing her husband truly is the killer, she takes the snake head to the zoo intending to tell Jack. Her husband follows her and ruthlessly throws her into the alligator pond, where she is devoured. The next day, some children sneak into the zoo and find a piece of her dress. Gorman identifies the garment and later attacks Jack with the snake head when Jack accuses him of the murder. Jerry arrives in time to administer the antitoxin, but Gorman escapes. He leads the police on a chase through the zoo, releasing all the big cats in the carnivore house. A lion chases him into a boa constrictor's cage, where Gorman is slowly killed by the huge snake. Jerry nurses Jack back to health, and the drunken Yates loses his fear of the big cats.