Bessie Wong

À San Francisco, le gangster Madden renonce au crime et se retire avec sa fille Molly, après avoir reçu les préceptes d'un philosophe de Chinatown, Chang Low. Un autre gangster, Mike Sylva, amant de Molly, complote alors pour mettre sur le dos de Madden un meurtre.

Sergeant Blake of the Northwest Mounted Police is sent to the border to break up a ring of smugglers who are bringing illegal Chinese immigrants into Canada. The ring is led by Ah Ming, a "half-breed" who goes by the name of Dr. Lawler. When Blake encounters Lawler, he is experimenting on a white mouse.

In Shanghai, an American girl who helps runs an opium ring meets an American agent disguised as a mining engineer. The two fall in love, and she has to determine where her loyalties lie.