Set in the western plains circa 1890, "A Dirty Western" opens upon a series of unique opticals and effects, depicting the escape of three dangerous convicts who have been imprisoned for seven years of a fifteen year sentence.
The story unfolds on a posse, made up of a sheriff and two prison guards, as they make their way through a snow storm in the high country. About a day ahead of the posse, the convicts have crossed the desert and are on the verge of dehydration. These scenes are accompanied by a dramatic ballad, composed and performed especially for the feature.
The story develops as a ranch-house in a hidden valley is revealed. The ranch belongs to Nate and Sarah Benson, their two daughters Lois and Maria, and Nate's sister Nancy.
Nate is unable to convince Sarah to go with him to the cattle sale because she must stay and prepare for the wedding of their daughter, Lois. Before he leaves, a sensuous love scene is portrayed between them.
Soon after Nate has left,
the convicts emerge above the hidden valley where they see the Benson ranch-house. Luke, the leader, leaves Ned and Barney and stealthily enters the house. He sees Nancy, Lois, and Maria bathing nude in a pond and Sarah approaching the house.
Sarah enters and is surprised at gunpoint by Luke, who warns her to be quiet and do as she's told or he will take it out on the girls. Luke quenches his great thirst and then brutally forces Sarah to submit to his animal lust.
Ned and Barney come down from the hill, drink from a rain barrel, and turn their attention to the girls. Sarah pleads for the girls and offers herself in their place. The convicts agree and a very savage and animalistic rape takes place in the shade of the barn.
While Ned and Barney are lusting Sarah, Luke re-enters the ranch-house and returns with a bag of gold and a change of clothes and supplies for him and his comrades. They hog-tie Sarah in front of the barn and leave, taking the nude girls as hostage. Nancy is allowed to carry a bundle of clothing for the girls.
Later, the posse finds Sarah at the ranch, cut her down and administer to her needs. At her insistence
the sheriff, who is a relative of the family, allows her to join the posse.
The long and wearying chase is taken up, intercutting between the posse and the convicts and girls. The trail has been easier for the posse to follow as Nancy has been cautiously dropping articles of the clothing she has been carrying. A powerful orchestration expresses and emphasizes this powerful sequence.
Because of their fatigue and exhaustion, the mood of the convicts and girls becomes temporarily happy and carefree when they arrive at a pond. They join in an orgy-like encounter in the water. The underwater photography is a, first of this type and is of great production value.
Continuing on their fateful journey, the convicts and girls climb to the safety of a cave high on the side of a mountain. Here, a deeply moving scene is depicted as Maria, the youngest daughter, loses her virginity to Luke.
Nancy overhears Luke exclaim to Ned and Barney that they should 'cool it on the sex or they will knock themselves out.' She secretly tells Lois and Maria that their chance to escape would be much better if they could sexually 'knock out' the men.
When the girls try to turn the convicts on, Luke forces them to perform an exhibition of lesbianism. Luke, Ned, and Barney become aroused watching the girls, and an erotic orgy ensues among them all.
Luke and Ned lie down to sleep, leaving Barney to guard the girls. The girls turn Barney on, and at the height of this encounter Nancy kills Barney with blows to the head from his own rifle butt.
In an exciting climax, Sarah, the sheriff and posse enter the cave, and in an exchange of gunfire, Luke and Ned are shot.
While Sarah and the girls join in a happy reunion, Luke, who is critically wounded, crawls toward his gun. Sarah sees him, picks up a rifle and cocks the hammer. A shimmering flashback depicts the cruel oppression brought upon her by this animal.
Sarah vindicates herself by slowly squeezing the trigger and killing Luke.