A group of communist spies plan to blow up an essential commercial artery, the Panama Canal. To this end, they have kidnapped a nuclear scientist and are traveling by steamship to the coast of South America. Luckily for western civilization, the hard-nosed ship's captain, played by Barton MacLane, has other ideas.

Humanoid killer robots stalk a newspaperman, who has knowledge of their existence. One of the robots is made to look like his girl friend.

A small town doctor mistakenly ingests an experimental drug made from the blood of vampire bats which transforms the kindly medic into a bloodthirsty monster.

When master monster make-up man Pete Dumond is fired by the new bosses of American International studios, he uses his creations to exact revenge.