The third of the Evil Dead Trilogy picks up where Evil Dead 2 left off, with Ash being sucked back in time to medieval England 1300 AD. There he finds King Arthur fighting a bloody war against the deadites, which are plaguing the land and Ash soon finds himself in a spot of bother, as he's mistaken for one of Arthur's enemies.
Fortunately, his trusty shotgun and chainsaw convinces them overwise and believing he might be the "chosen one" as fortold in the Necronomicon (The Book of the Dead) a bargain is struck. If Ash can retrieve the book from the deadites, that will allow Arthur to defeat them and that will also allow them to return Ash to his own time.
However, to do this, he has to recite the magic words "Klaatu Barradda Nikto", before removing the book from its resting place. Unfortunately Ash, who's not the brightest of hero's, gets the words wrong and although he retrieves the book he also awakens the army of the dead.
And so the scene is set for a battle of medieval proportions, as the deadites attack Arthur's castle, and Ash helps to defend it, with a bit of 20th century know-how. Which includes making home made bombs, self defence classes and Ash mowing down deadites in a steam powered Oldsmobile.
As you can probably gather, the sense of humour in this film is far more prevalent than in the other Evil Dead Films. A lot of fans who liked the previous 2 movies where sadly disappointed by the comic twists in this third instalment. But I personally thought the extra humour worked very well, and believe Army of Darkness to be the best in the Trilogy. When you look at this film, you can see where Sam Raimi and producer Robert Tappert got the idea for their "Hercules" and "Xena" TV shows (which not-so coincidentally also star Bruce Campbell).