After gangster Mulligan's cars colony, fleeing northern justice, finds a hiding place in Alabama, spoiled, naive daughter Grace refuses to travel on after seeing the Manderlay cotton plantation being run under slavery rules, called Mam's law, inclusive flogging. She keeps half of dad's goons as guard to force the dying matriarch-owner's heirs, which she shamelessly dispossesses and reduces to 'staff', to taste destitution under absurd, gun-imposed contracts. The 'slaves' are made free partners, supposed to vote for progress after lessons from Grace. But almost all her democracy-pupils prove fickle, dumb and selfish, except old Willem. Her and their ignorance in Southern planting and crafty Dixie ways means more problems are created then solved. By the time dad returns to pick her up or abandon her for good, she's the one who has learned and changed the most.