A supermarket employee, Ash Williams, finds himself transported to the medieval past along with his car, his shotgun, and a chainsaw that conveniently replaces his missing hand. Having already battled the undead in his own time, he is unprepared for the new setting but quickly proves his worth by killing a Deadite, a monstrous being animated by evil spirits. The people of the medieval kingdom, initially mistaking him for an enemy, soon come to believe he is "The Chosen One" foretold to rescue them from the demonic scourge. Reluctantly, Ash agrees to help them in his quest to return home.

To vanquish the Deadites and find a way back to his time, Ash must secure the Necronomicon Ex-Mortis, a book with the power to banish the evil. However, obtaining the Necronomicon is no simple feat; Ash must utter specific words correctly to safely retrieve the book. His failure to remember the words properly unleashes an evil force, complicating his mission. Caught in a battle of survival, Ash must use his modern-day wits and weaponry to defeat the supernatural forces, win the trust of the kingdom's inhabitants, and find a way to return to his own time.