Cassie Cook has been selling opium in Shanghai but bad luck has compelled her to team up with her biggest rival, Jules Repin. The horror of the opium trade weighs on her and she determines to quit the trade and leave China before it is too late. Believing in Repin's promise that he has a big shipment of opium coming in, she has bought a lot of new gowns on credit and is unable to pay for them. She also needs money to pay for passage home for a friend, Molly Morton, whose growing opium habit has left her an invalid.
After betting on a "sure thing" in the races and losing, Cassie determines to make her way to Hang Chow, a trouble-infested village near the poppy fields, to try to trace the opium shipment Repin expected. There she finds Captain Arthur Jarvis, who is supposed to be opening an abandoned mine but is in fact a government inspector seeking the den of the dope dealers. Cassie poses as a novelist, and Jarvis, who is attracted to her, reveals his true mission. Cassie, who has fallen in love with Jarvis, is on the verge of telling him all when Repin and his Chinese confederates arrive and stir up local rebels against Jarvis. The rebels attack and set fire to the settlement. Repin, on the verge of killing Jarvis, is shot by Rose Li, the daughter of one of Repin's associates, who is also in love with Jarvis. Jarvis and Cassie escape, taking with them the young son of a missionary.