It is 1937 and Shanghai is under Japanese occupation. Walter Faraday, known as "the Opium King" and a supplier named Mei Gan battle over a valuable supply of the drug and Faraday is killed. A year later, missionary Gloria Tatlock comes in search of Faraday's legendary opium to relieve the pain of injured soldiers. She and her fellow missionary need a street-wise man to help them in their quest and they engage the fortune hunter Glendon Wasey. The vulgar Wasey finds himself in a dangerous adventure with less than pious Tatlock and before long they both find themselves falling in love.