"On a winter night on a remote Nebraska road, twenty-seven-year-old Mark Schluter has a near-fatal car accident. His older sister, Karin, returns reluctantly to their hometown to nurse Mark back from a traumatic head injury. But when Mark emerges from a coma, he believes that this woman--who looks, acts, and sounds just like his sister--is really an imposter. When Karin contacts the famous cognitive neurologist Gerald Weber for help, he diagnoses...

Plant-like extraterrestrials have invaded Santa Mira, a small town in California, replicating the villagers in giant seed "pods" and taking possession of their souls while they sleep. Dr. Bennell finds that his patients are becoming hysterical and accusing their loved ones of being mindless imposters. Realizing a strange alien invasion is quickly becoming out of control, the doctor tries to escape to warn others before it's too late.