While working as a night waitress on the San Francisco dockside, Helen Roberts meets Martin Rhodes, a schooner captain. Martin is waiting for Mario Rigo, a friend's brother, to discuss a mysterious cargo shipment. Because she is on probation for a crime she committed unwittingly, Helen is at first wary of Martin, but finally gives in to his charms and agrees to spend an afternoon with him, unaware that he is being followed by gangsters George Skinner and Dorn. When Martin glibly confesses his past as a rum- and gun-runner, Helen expresses her disapproval and, as they watch the construction workers on the Golden Gate Bridge, tells him she would like him more if he had a decent, honest job. The next night, Rigo shows up at Helen's restaurant and is surrounded by Skinner, Dorn and two other gangsters, who have been sent by Borghum, a phony private investigator, to track down the shipment. Before being shot to death, Rigo scribbles a map on a napkin and slips the napkin to Helen with instructions to pass it on to Martin. After the shooting, Helen is taken to police headquarters for questioning but, in spite of the police's tough interrogation, remains silent about Martin. When she returns home, however, she is attacked by Skinner, who struggles with her for the napkin and eventually falls out of her window to his death. Followed by Dorn, Helen finds Martin at his schooner and, after assuring herself of his innocence, reconstructs Rigo's cryptic map from memory. Together Helen and Martin interpret Rigo's map and determine that he planted a shipment of stolen gold under the schooner. Dorn, meanwhile, notifies Borghum about Martin's whereabouts, and just after Martin leaves to present his discovery to the district attorney, the gangsters take over the boat. Eventually Martin traces the schooner by following a trail of oil left by his shipmate, Fong, and the gangsters are apprehended. Cleared of all suspicion, Martin and Helen declare their love.