A wealthy young man, Rollo Treadway, decides on a whim to propose marriage to his neighbor, Betsy O'Brien. When Betsy declines, Rollo decides to take a solo honeymoon to Honolulu. However, through a mix-up, he boards the wrong ship, the Navigator, which coincidentally Betsy’s family has just sold to a foreign government. Betsy ends up on the ship as well after a failed attempt by her father to retrieve important papers. Unbeknownst to Rollo and Betsy, the Navigator is set adrift by enemy agents, leaving the two stranded and alone in the middle of the ocean.

Isolated and with no idea how to operate the massive ocean liner, Rollo and Betsy struggle to adapt to life aboard the Navigator. They try to find their way through the ship’s many compartments, facing various challenges and learning to work together despite their initial ineptitude. They also have to deal with the potential danger posed by any enemies who might be lurking. Throughout their ordeal, their relationship evolves as they rely on each other for survival.