In 1878 in the south west of the US, Ben Nicholson is the richest rancher of the area. A tough man who strikes a hard bargain, he has been outwitted by his second wife Katherine, a flirtatious intriguer. Of his two sons from the previous marriage, Frank is gay and the unfortunate David is a half-wit. There is a third son in the house however, born from the black cook Marpessa, who acts as butler: this is Whity.
Despite his capability, Whity gets humiliated and whipped. His only hope of any decency lies in his friendship with the town's saloon singer and whore, Hanna. She has landed a job back in the east and offers to take Whity with her, but he says he must stay with his family.
To trap Katherine, Ben arranges for a Mexican called Garcia to pretend he is a physician and to seduce her, confiding to her that Ben has not long to live. The plot succeeds but, rather than pay what he promised, Ben kills Garcia. When he learns that Hanna witnessed the murder, he pays her for her silence.
Excited by the prospect of inheriting the ranch, both Frank and Katherine try to get Whity to kill Ben. In the end, after repeated humiliations in a household where everybody is trying to seduce or kill each other, Whity decides he must at last act. He shoots all four Nicholsons and flees into the desert with Hanna, whose money he had earlier stolen and gambled away. When they eventually run out of water, they dance together as the sun sets behind them.