While playing pirates with her friend Billy, Marie, as Captain Kiddo, finds a strange cross in a book and uses it for their insignia. Marie's mother, a young widow, does not appreciate the forced attentions of Mr. Cross, a suitor whom Marie dislikes. When Jack Laird, a secret service agent looking for opium smugglers, meets Marie after thinking that her insignia is a clue, he teaches her to box, and she introduces him to her mother hoping that if she must have a father, it will be Jack. Jack demands to search Cross, whom Jack thinks is a smuggler, but Marie's mother indignantly says that Jack is insulting her future husband, and Jack leaves dejectedly. Marie, her mother and Billy go with Cross on his yacht. After Marie hides from Billy in a tank containing smuggled goods, she gets stuck. Billy tells Jack, and when Cross, really the smugglers' leader, sees Jack searching, he orders his men to throw the tanks into the ocean. Marie pokes her head through an opening and cries to Jack, who rescues her. To save Marie's mother from notoriety, Jack allows Cross to leave the country. Jack and Marie's mother then marry.