First came the news headlines that a flying saucer had landed in Iowa. After that came the announcement that the whole lot was a hoax. End of story. Case closed.

Except that two agents of the most secret cleverness agency in the US government were for the picture and disappeared without reporting in, as did four other agents who were sent in. Because of this, the head of the agency and his two top agents proceeded to go in, plus they got out using their discovery: the planet earth has been invaded by slug-like aliens who about The Puppet Masters can completely control the mind of any human being they touch. What the humans know, they know. The actual aliens want, no real matter what, the individual will do. & most of Iowa has already been under their control.

Sam Cavanaugh was one of the agents who discovered the truth. Unfortunately, that was right before he was bought out by among the aliens and began doing work for the invaders, without will of his very own. And he has just learned that a high standard in the Treasury Department is now under control of the aliens. Because the Treasury Department includes the Secret Assistance, which safeguards the president of america, control of the entire nation is normally near accessible. Can-do intelligence official Cavanaugh is the only man who can end the invaders.