In the first ten seconds, slave breeder James Mason observes, about a slave starlet, "She’s Mandingo wench. You don’t let just any bud get her," to remind his crippled son, Perry King, of his family obligation. Local doc Roy Poole agrees, saying, "She’s craving, in the bud o’ heat. You pleasure her, she get better." The slave starlet tries to stall the inevitable by drawling to King, "I too black, I not fit for you." Mason settles the matter by stating, "Master’s duty to pleasure the wenches first time."
Then it’s back to the family mansion, where Doc Poole suggests that Mason’s rheumatism would improve if he’d put his feet on black children. So for the rest of the movie, Mason (astoundingly) uses two little slave lads as his foot stools.
King brings home a new stud slave, Ken Norton, another slave to be King’s mistress, Brenda Sykes, and — last but not least — a Southern belle whom King will marry, Susan George. King tells his pa, Mason, that Norton is "hung so big he’ll tear the wenches," then orders Norton to "shuck down those pants!" When the wedding night’s a bust — King sneers at George, "you thinkin’ I don’t know a virgin when I sleeps with one and pleasures?" — King turns to Sykes, driving George into Norton’s bed.
Mason tells George that to win King’s affection back, she should "do dirty things to get him in your bed and keep him there." Instead, George — whose incestuous relationship with her brother is her Big Secret — screams at King about Sykes, "That slut! You like black meat? You’d rather pleasure with a baboon?" and then (there’s more), when George learns Sykes is pregnant, she hisses, "You dumb animal!" and pushes Sykes down the stairs. Later, George discovers she’s preggers and — as the doctor’s wife so eloquently puts it after the delivery — "It come, only it ain’t white."
King cheers us up by promptly poisoning George, then finds the baby’s real dad, Norton. You’re not going to believe this — we didn’t — King settles the score by shooting Norton, then pushing him into a vat of boiling water, and then pitchforking him to death. In retaliation, one of Norton’s pals shoots and kills Mason, ensuring that he wouldn’t be able to overact in the sequel, Drum.