At key locations across the North American continent, an invasion force is taking over communications, government, industry, and even people’s bodies. The nation is helpless to stop it because the invaders multiply far faster than they can be destroyed, controlling the mind of every unsuspecting person they encounter. Enter Sam Cavanaugh, a can-do intelligence officer for the United States’ most secret service. Cavanaugh is the only man who can stop the invaders. But to do that he’ll have to be invaded himself.

ROBERT ANSON HEINLEIN (1907–1988) was born in Missouri. He served five years in the U.S. Navy, then attended graduate classes in mathematics and physics at UCLA, took a variety of jobs, and owned a silver mine before beginning to write science fiction in 1939. His novels have won the Hugo Award, and in 1975 he received the first Grand Master Award for lifetime achievement.