Having unexpectedly found himself transported back to the Middle Ages, Ash Williams becomes embroiled in a conflict when he is captured by the soldiers of Lord Arthur, who suspect him of being a spy for the enemy Duke Henry. Enslaved alongside the captured Duke, Ash has his beloved shotgun and chainsaw taken from him and is confined to Arthur's castle. However, resilience shines through when Ash is thrown into a pit where he makes short work of a Deadite, reclaiming his weapons thanks to Arthur's Wise Man. With a bold demand for the freedom of Duke Henry and his men, Ash's valor earns him the admiration of the townsfolk, who hail him as a hero. During this time, he finds himself attracted to Sheila, the sister of one of Arthur's slain knights.
The Wise Man informs Ash that the key to returning to his own time lies within the mystical Necronomicon Ex-Mortis. Thus begins Ash's perilous journey to find this ancient book. As he ventures into a haunted forest, he is relentlessly pursued by an unseen force until he crashes into a windmill. There, he encounters eerie reflections of himself in the shattered mirror that spring to life and turn against him; one particularly troublesome reflection is dismembered and buried by Ash.
Upon reaching the location of the Necronomicon, Ash is bewildered to discover three different books instead of the single tome he sought. Just as he realizes he has forgotten the crucial last word of the incantation necessary to retrieve it — "Klaatu barada nikto" — he frantically tries to mumble his way through the words. He seizes the book and hurries back, unaware that his doppelgänger has been resurrected and is uniting the Deadites into the formidable Army of Darkness.
When Ash returns, he insists on being sent back to his own time. However, events take a dark turn when Sheila is captured by a flying Deadite and subsequently transformed into one by the malevolent Evil Ash. Undeterred, Ash vows to rally the local humans against the looming threat of the Deadite army, who reluctantly agree to follow him into battle. With a trusty knowledge gleaned from textbooks stored in his 1973 Oldsmobile Delta 88, along with the assistance of Duke Henry, Ash successfully leads the outnumbered soldiers to an overwhelming victory against the Deadite forces, defeats Evil Ash, rescues Sheila, and brokers peace between Lord Arthur and Duke Henry.
The Wise Man, equipped with a passage from the Necronomicon, provides Ash with a potion that will facilitate his return to the present, contingent upon reciting the original incantation once more.
Upon his return to modern times, Ash excitedly shares his incredible tale with a co-worker at the S-Mart department store. In the midst of recounting his experiences to a female colleague interested in his adventures, a lurking Deadite appears, thanks to Ash's unfortunate slip of memory regarding the incantation. With quick reflexes, Ash dispatches the creature using a Winchester rifle, triumphantly declaring, > "Hail to the king, baby," before sealing the moment with an enthusiastic kiss for his co-worker.
