Sadie Martin owns a riverboat that is frequently used by miners traveling to their claims. During their trip, the miners drink and gamble. Sadie's daughter, Helen, is unaware of her mother's work because her mother sends her to boarding school in order to live a lifestyle more attributed to the upper-class. Unfortunately for Sadie, she is facing difficulty maintaining the costly riverboat. She is soon forced to sell the boat in order to make ends meet.

Scientists pursuing the mysteries of the deep are threatened by a beautiful girl who seems to have returned from the dead and by a prehistoric sea creature.