In the early 1890's, on a Mississippi River steamboat, an orator calling himself the "New Moses" preaches against the evils of "demon rum." Shortly thereafter, Dr. John Pearly hawks concoctions he calls "Pocahontas Remedies," which seem to have a high alcoholic content. After Doc buys the steamboat Claremore Queen with the money he has made selling the "remedies," steamboat Captain Eli of the Pride of Paducah wagers his boat against Doc's in the upcoming race to Baton Rouge. Doc is a bit chagrined to find his boat in a delapidated state, but he makes Efe, an alcoholic who owes him for a number of bottles, his engineer and first mate and puts him to work. Doc plans on having his nephew Duke, the pilot of the Memphis Belle , run his boat, but Duke arrives with a "swamp gal" named Fleety Belle, with whom he is in love, and confesses that he killed a man who attacked her. When Doc learns that the New Moses was a witness, he convinces Duke to give himself up to the sheriff, because Duke struck the death blow when the man came at him with a knife. Doc promises to take care of Fleety Belle. After he calls her "swamp trash," she tries to stab him, and Doc gains admiration of her spunk. When her father, fiancé and brother try to take her off the boat, Doc tells them that she and Duke are married and then chases them off with a kitchen knife. Doc then gives the grateful Fleety Belle an outfit that belonged to his deceased sister, Duke's mother, to wear to court instead of the tablecloth she wears. The judge rules against Duke, however, and Doc sends to Baton Rouge for a good lawyer for Duke's appeal. When the sheriff shows Doc an abandoned wax museum, Doc gets an idea to put the museum on his steamboat and put on a traveling show to raise the five hundred dollars for the lawyer. Although he raises the money, the court turns down Duke's appeal, and when the sheriff is about to take him to Baton Rouge, where he is to be hung, Fleety Belle grabs the sheriff's rifle and Doc grabs the sheriff, urging Duke to run. Duke, however, remains rather than get them into trouble. Doc vows to find the New Moses, but he has no luck, and with only two days before the hanging is to occur, he decides to go to Baton Rouge and speak with the governor, with whom he fought at Shiloh during the Civil War. On the way there, they are stopped at the beginning of the steamboat race to Baton Rouge. Challenged again by Captain Eli, Doc enters the race, and when they see the New Moses preaching by the shore, Doc lassoes him and pulls him into the boat, where Doc convinces him to testify on Duke's behalf. The New Moses helps with busting up the deck and lifeboat for firewood, and during the evening, Doc throws a lasso to hook unto Captain Eli's boat to pull them until morning. The next day, after Eli orders the rope chopped off, the Claremore Queen runs out of wood, so Doc suggests that they burn the wax figures from the museum. Despite this, Eli's boat still leads, until the New Moses sees Efe take a swig of the Pocahontas Remedy and, deeming it "demon rum," throws it into the furnace. The resulting explosion leads Doc and the others to toss in the remaining one hundred jugs, except for one which Efe hides, and the Claremore Queen pulls ahead of the Pride of Paducah and wins. With the New Moses in tow, Doc convinces the governor to stop the hanging, and soon Duke and Fleety Belle pilot the Pride of Paducah together.