This is the second in a series of movies that exist in a strange subset of Mystery / Detective movies where the detective is of Oriental decent. You know, because people from the East have superior and almost mystic deductive qualities, perfectly suiting them to work as detectives for crowded cities in the USA.
Anyway, this Mr. Wong series is pretty good. Boris Karloff (Born in London, not Asian at all) plays Mr. Wong, and in this one a chemical manufacturer comes to detective James Wong for help, fearing his life is in danger. Like most of the people you’ll see coming to Mr. Wong for help, he is shortly after murdered. As Mr. Wong investigates, he uncovers an international spy ring in the midst of stealing a secret formula for poison gas.