A brother and sister, Barbra and Johnny, visit their father's grave in rural Pennsylvania, only to be suddenly attacked by a strange man. In the chaos, Johnny is killed, and Barbra flees, finding refuge in an isolated farmhouse. There, she's later joined by Ben, who fortifies the house from the advancing menace – reanimated corpses, or 'ghouls,' with an appetite for human flesh. As the two try to comprehend the situation, they discover a television and radio, delivering fragmented news reports of the rising dead across the nation, positing that radiation from a fallen space probe might have instigated the ghastly phenomenon.

Inside the farmhouse, tension arises when they encounter five others hiding in the cellar: Harry and Helen Cooper, their daughter Karen, and a young couple, Tom and Judy. Conflict surges over the best course of action – to stay barricaded in the cellar or defend the upper levels of the house. The group's dynamics become strained under the pressures of survival, with individual philosophies and fear dictating their interactions. Outside, the undead amass in greater numbers, encircling the house, with the survivors' chances of escape and survival diminishing with each passing moment.