<span class="SFPTagline"> From SCIFIPEDIA </span>

The Puppet Masters (1951) by Robert A. Heinlein. The fear of invasion is a bone-deep human emotion. Invaders are aliens, and they mean no good to those they usurp. Heinlein literalizes that fear in The Puppet Masters, a tale in which the alien invaders are so alien they're not even native to our planet. Their most fearsome characteristic is that they can remake anyone, no matter how well known--a friend, a lover, a parent--into a cold-hearted alien being, too.

The hero is Sam Cavanaugh, a secret-service officer and one of Heinlein's trademark Competent Men. Sam's boss, the Old Man, is also his father. The Old Man assigns Sam to assist another agent, Mary, in investigating reports of a space ship landing in Iowa. Sam, Mary, and the Old Man find out that sluglike alien creatures the size of footballs are attaching themselves to people's backs. The slugs take over the humans' brains and control them in every way…