Ash Williams and his girlfriend, Linda, take a romantic vacation to a seemingly abandoned cabin in the woods. While in the cabin, Ash plays a tape of archaeologist Raymond Knowby, the cabin's previous inhabitant, reciting passages from the Book of the Dead, Necronomicon Ex-Mortis, which he has discovered during an archaeological dig. The recorded incantation unleashes an evil force (also known as the Kandarian Demon) that kills and later possesses Linda, turning her into a "deadite". Ash is then forced to decapitate his girlfriend with a shovel and bury her near the cabin.
At dawn, the evil force throws Ash through the woods. Ash briefly becomes possessed by the demon, but when day breaks the force is gone, and Ash returns to normal. Ash attempts to flee the area, but finds that the bridge leading to the cabin has been destroyed. The spirit chases Ash back to the cabin where Linda's revived head attacks him, biting his hand. Ash brings Linda's severed head to the shed, where her headless body attacks him with a chainsaw. Ash gains the upper hand and slashes the deadite Linda to death, killing her a second and final time. Ash's right hand becomes possessed and tries to kill him, and Ash severs it with his chainsaw. Ash then attempts to shoot the severed hand with a shotgun. The hand mocks him and ultimately gets away.
Meanwhile, Knowby's daughter, Annie, and her research partner, Ed Getley, return from the dig with the missing pages of the Necronomicon in tow, only to find the destroyed bridge. They enlist the help of locals Jake and Bobby Joe to guide them along an alternate trail to the cabin. The four of them find an embattled Ash at the cabin. Mistakenly concluding that Ash murdered the Knowbys, they lock him in the cabin's cellar.
The four new arrivals listen to a recording of Knowby detailing that his wife Henrietta was possessed by the Kandarian Demon, and that he killed her and buried her in the cellar. Henrietta, now a deadite, possesses Ed; Ash dismembers him with an axe. Bobby Joe tries to escape but is attacked by the demon trees and dragged to her death. Annie translates two of the Necronomicon's pages before Jake turns on them and throws the pages into the cellar, forcing them at gunpoint to go look for Bobby Joe. Ash becomes possessed once again and incapacitates Jake. Annie retreats to the cabin and accidentally stabs Jake (mistaking him for the possessed Ash) and drags him to the cellar door, where he is killed by Henrietta. Deadite Ash tries to kill Annie, but returns to his normal self when he sees Linda's necklace.
