Skin Game (1971)

Quincy Drew and his black friend Jason O'Rourke have pulled off every dodge known for conning a well-heeled sucker, but it wasn't until they hit on the old skin game that they started to clean up. The game is simple. Jason, though born a free man in New Jersey, poses as Quincy's slave as the pair ride through Missouri and Kansas in 1857. Quincy picks a likely mark in each town, sells Jason to him for top money and rides out of town. Then Quincy and Jason get back together on the road to another town, because if Jason can't just run off after dark, Quincy finds a way to spring him loose.