Mid-19th century: Mark Fallon (Tyrone Power), a professional gambler, is one of the few honest players on the Mississippi's floating casinos. When he wins a valuable diamond necklace and flees to New Orleans, he witnesses its previous owner, Angelique (Piper Laurie), become the object of his desire and become involved with a banker. At least Mark opens a successful casino with Angelique's father. But even there, he cannot find his true happiness.