 Chinese businessman Han Wu Ling has discovered a map leading to the location of a long-lost silver mine. He agrees to sell it to the London and Shanghai Bank, where Lord Pearson has called a meeting of the board of directors in order to purchase the map. But Mr. Wu Ling fails to attend the meeting, and is later found dead in Chinatown. The lead suspect, an American stock investor and speculator, is found with Mr. Wu Ling s passport. But nothing is simple as the investigation leads to opium dens, drugs, gambling, and the seedy underside of life in London.