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.

Silent Madden and his daughter Molly have left the criminal underworld of San Francisco thanks to the wise teachings of Chang Low, a Confucian master. But the evil Black Mike Sylva is determined to frame Madden to avenge a mistake from the past…