Dr. John Pearly is an affable turn-of-the-century con man who sells a patent medicine that is mostly whiskey. He resurrects a broken down steamboat with a makeshift crew and challenges the respectable but arrogant Captain Eli to a winner-take-all river race. Pearly hopes his nephew Duke will serve as pilot, but he stands accused of murdering a 'swamp rat' who threatened the honor of swamp girl Fleety Belle. After Duke is arrested, Pearly tries to raise money for a lawyer by displaying a wax museum aboard ship. Ultimately he gambles it all in the river race to Baton Rouge, where he hopes to find a witness whose treatment will free Duke.