Having been the guest star in "Charlie Chan at the Opera," Boris Karloff takes his own turn at being a brilliant Chinese detective in "Mr. Wong, Detective," in an obvious effort by Monogram, a poverty row studio, to capitalize on the popular Charlie Chan series. When Simon Dayton (John Hamilton), a chemical manufacturer in San Francisco receives anonymous death threats after his company begins making poision gas, he seeks the help of James Lee Wong. Of course, the next day the man is killed by his own gas, quickly followed by two of his business partners. Soon Mr. Wong and Police Captain Street (Grant Withers) are on the trail of a group of foreign spies who want to steal the formula for the poison gas.
This is an okay mystery of this type and I really thought they came up with a rather ingenious way of delivering the poison gas (remember the fear that people had of such a weapon after World War I). The plot is better than the acting, but that is standard for a film put out by Monogram (they did sixteen John Wayne B Westerns earlier in the decade). This 1938 film was directed by William Nigh and is based on the stories of Hugh Wiley, and gave Karloff something to do besides monster movies. You do not really buy that he is Chinese, but he does bring a certain dignity to the role, which is nice to see given the time when this film was made.
Ironically, while the Mr. Wong films were made to capitalize on the success of Charlie Chan and Mr. Moto, "Mr. Wong, Detective" was remade in 1948 as a Charlie Chan film, "Docks of New Orleans" (when Monogram finally bought the rights to the series they apparently had no money left to buy a new script). There were six Mr. Wong films, all made relatively quickly and cheaply. As you would expect, if you have seen one you have essentially seen them all. They are minor diversions at best.