Sadie Martin, the hardboiled mistress of the Yukon Queen riverboat, deals cards to the miners of the Yukon as her boat transports them up and down the river. When her daughter Helen leaves her Eastern boarding school to pay a surprise visit on her mother, Sadie attempts to hide her profession from the girl. However, Helen becomes infatuated with the romance of the Yukon and, upon discovering her mother's profession, decides to emulate her. Determined to rear the girl properly, Sadie sells her boat to Thorne, the crooked manager of the Yukon Mining Company who is scheming to seize the miners' lands and claim them for himself. Thorne's unwitting instrument in his scheme is Bob Adams, a young surveyor who has fallen in love with Helen. Upon learning of Thorne's treachery, Sadie and Ace Rincon, the miner who has loved Sadie for years, rally the miners to fight Thorne, but before they can act, Thorne steals the claim papers and sends them "down the river" with the unsuspecting Bob. When Bob learns of Thorne's duplicity, he pummels the claim jumper, thus winning Helen's love and admiration for his bravery. After Ace forces Thorne's confession, Helen accepts Bob's marriage proposal, and Sadie finally agrees to marry Ace.