Fast talking con man Martinus Van der Brig persuades Grey Holden and Bill Blake, the riverboat's new pilot, to transport a group of pioneers to a land he recently purchased named Rolling Stone. Van der Brig has sold the pioneers on this territory as a land of plenty and wonder, but that is far from the truth.
When Grey Holden loses the money in a crooked card game, the sheriff of Baton Rouge impounds his riverboat so that the vessel can be sold to pay off his debts. Grey is forced to sell a half-interest in the Enterprise to his pilot, Bill Blake to prevent the auction, then, to gain enough capital to stay in business, Holden and Blake hatch a wild scheme to hijack President-elect Zachary Taylor and his party who are bound for Washington D.C. and his inauguration.
When a pretty Cajun girl catches Captain Holden's eye, he's naturally interested in a bit of romance, until he learns that the young lady thinks he is her fiancée, who was killed in a riverboat explosion over a year before.
After the Glen City sheriff runs him out of town, boxing promoter Dan Muldoon convinces his old friend Grey Holden to host a prize fight on the Enterprise. When Grey Holden knocks out Muldoon's fighter, The Dublin Boy, by accident, he is forced to take the young man's place in the ring or he'll have to return the gate receipts to a boat-full of angry passengers. Meanwhile, a couple of thieves plan to steal all the money that has been wagered on the bout.
On a dark and stormy night, the Enterprise smashes into a recently built railroad bridge that spans the Mississippi River. Grey Holden and Bill Blake sue the railroad company for damages but must best a long-legged legal beanpole named Abraham Lincoln in court before they can repair their riverboat.
En route to a popular fair, Grey and Bill accidentally book for passage two families of hillbillies who are engaged in a murderous feud. The Cox and Jennings families proceed to shoot up the Enterprise with the riverboat's crew caught in the crossfire. Holden desperately tries to negotiate a truce before a passenger or crew member gets hurt.
An army sergeant, determined to meet his quota for new recruits, forces one of Captain Holden's crewmen into his platoon by hitting him on the head. When Holden comes to confront the sergeant, he too is shanghaied.
While carrying a cargo of gunpowder, Holden and his crew witness a band of Mexican outlaws executing a man by the river. When they come to the town of Chicota Landing they learn that the man killed was a deputy to the sheriff, who is holding the leader of the outlaws, Juan Cortilla, in his jail cell. The town's citizens try to storm the jail for a lynching, during which Cortilla escapes. Later an Army lieutenant asks Holden to use the Enterprise to bring Cortilla and his band to a military garrison. But Cortilla soon takes over the Enterprise, along with the gunpowder...
Captain Holden and the Enterprise crew find themselves caught between ruthless Brian Cloud, who monopolizes all the cotton crop in the area, and Laurie Rawlings, the wife of a cotton planter, who doesn't like her husband being under Cloud's control.
While in a town doctor's office trying to pull Carney's aching tooth, Bill Blake is abducted by three outlaws who mistakenly think he is the doctor. They want him to treat a dying old man who they believe knows the location of a large amount of money. When they realize he is not a doctor, they ask him to pretend he is the old man's son to get him to reveal the location of the loot. To make him do this they threaten the life of the owner of the cabin they are hiding in, along with his pretty daughter.