The nominal plot involves five vacationing college kids -- Ash (Bruce Campbell), his girlfriend Linda (Betsy Baker), and their classmates Cheryl (Ellen Sandweiss), Scott (Hal Delrich) and Shelly (Sarah York) -- making an unplanned stopover in an abandoned mountain cabin surrounded by impenetrable woods. Before settling in for the night, they come across an ancient-looking occult tome filled with dense hieroglyphics and macabre illustrations, a dagger fashioned from human bones, and a reel-to-reel tape recorder. The taped message, dictated by a professor of archaeology, describes the contents of the Sumerian "Book of the Dead," filled with incantations used to bring otherworldly demons to life, giving them license to possess the living. The message goes on to explain that those possessed by these demons can only be stopped by total bodily dismemberment. When played among the group later that evening, the professor's recorded translations of the ritual chants traumatize the strangely prescient Shelly ... and simultaneously release an ominous presence from the depths of the forest. The evil spirits take to their dirty work with gusto, first assuming control of Shelly and transforming her into a cackling, murderous hag with superhuman strength; the others imprison her in the fruit cellar and chain the trapdoor shut. The spirits then begin to possess the other women, including Linda -- who immediately turns on Ash with a barrage of punches and sadistic taunts. Unable to bring himself to chop up his lover's corpse, Ash gives her a more customary burial in the woods -- which proves to be a big mistake. As the others succumb to demonic influence, Ash's horrific predicament becomes increasingly grim until, when all hope seems lost, he stumbles upon a final, desperate solution to the ghoulish onslaught...well, maybe not.