Barbra and her brother, Johnny, start off the movie driving to Pennsylvania to visit their father's grave. Upon reaching the cemetery, they are met by a strange man, who attacks and kills Johnny. The car that the two came in starts having problems, so Barbra escapes the man on foot, eventually ending up in house with a man named Ben, who always carries a rifle with him. That night, Barbra believes she is going insane, and slowly falls into a pit of madness.
Ben, despite seeming very confident, admits that he knows nothing about what is happening. He also sought refugee in this house, and discovers that it has a cellar. In the cellar reside the Cooper family, made up of Harry, Helen, and their daughter Karen. They sought refugee here after similar monsters attacked them. Tom and Judy, a younger couple, also arrive on the scene.
Hearing radio reports from their spot in the cellar, it is stated that a wave of murders is sweeping the United States, but no one knows exactly what was going on. Everyone in the cellar seems to want to stay there except for Ben, who deems it a "deathtrap". He proceeds outside with Tom to seal up the house better.
Attempting to seek refugee at a local shelter that they heard about on the radio, Tom, Judy, and Ben head out in a truck. Stopping at a gas station, the undead start to attack the group, but Harry hurls cocktails at them. Tom spills gasoline, and the Truck sets fire, and both Tom and Judy die. Ben returns to the cellar, but Harry is afraid to open it for him. Ben breaks in, and hits Harry in his anger.
The cellar's lights go out, and the zombies break in. Much commotion ensues, and Ben is the only one left alive. He seals himself in the cellar once again, but the zombies continue to try to break in. Outside, gunshots can be heard, and Ben is relieved that someone has come to save him. However, Ben is mistaken for one of the monsters, and brutally shot to death.
