The Japanese spy, Kawakami, desiring to learn the whereabouts of Fred Langford, an inventor who is perfecting a marvelous device for the defense of his country, and who has suddenly dropped out of sight, kidnaps Langford's wife upon her arrival in San Francisco. He forces from her the secret of her husband's hiding place. He then sends a note to Langford, ostensibly from blackmailers, demanding that he bring a certain sum of money to a certain place in Chinatown, hoping in this way to get the inventor in his power and to force from him the secret of his latest device. A member of the secret service has witnessed the kidnapping, however, and the plan of the Japanese being suspected, Francis Gordon is put on the case. He is assisted by a female operative, Barbara Ward, who is also his sweetheart. Barbara disguises as a Japanese and obtains admittance to Kawakami's house, where she finds Rose Langford. She succeeds in spiriting Rose out of the place, but is herself caught by the Japanese spies. Gordon, sending the car containing Rose Langford speeding away to safety, forces an entrance into the house and rescues Barbara. Barbara, however, dies from wounds she receives in the struggle.
—Moving Picture World synopsis