U.S. Secret Service agent Truxton Darnley attires himself as a sailor and boards a schooner owned by Gus Olsen, who has been employed by a German spy named Von Linterman to smuggle arms to German raiders in the South Seas. During the voyage, Truxton learns that Gus and his men plan to blow up the National Munitions Plant in San Francisco, but Gus discovers his identity and throws him overboard. Truxton is washed ashore on the island of Moana, where he meets and falls for Lurline, the daughter of beachcomber "Brandy" Cain. Promising to return to her, Truxton boards a steamer bound for San Francisco in the hope of saving the munitions plant, and soon afterwards, Brandy sells Lurline into marriage with Gus. Seeing Truxton's steamer, Lurline dives from Gus's schooner, and her sweetheart rescues her. In San Francisco, Gus abducts Lurline and forces her to dance in his Barbary Coast saloon, but Truxton and his men raid the bar, and Gus is killed. After receiving the happy news that her real father is the owner of the munitions plant, Lurline joins Truxton, the man of her dreams.—AFI