The teenager Marti Malone is traveling along her summer vacations with her father, the EPA inspector Steve Malone, her stepmother Carol Malone and her young stepbrother Andy to a military base where her father will inspect some toxic products. In a gas station bathroom on the road, she is scared by a soldier that advises her to not sleep, because they get you when you sleep. Once in the base, she becomes friend of Jean Platt, the daughter of the general in charge of the base, and the helicopter pilot Tim Young. Marti and her father see that people are acting strange, and sooner they find that aliens are cloning the human beings in the base and invading Earth.