Mr. Wong, Detective

Mr. Wong, Detective is a 1938 American crime film directed by William Nigh and starring Boris Karloff in his first appearance as Mr. Wong.

Among the suspects are agents of a foreign power wishing to stop Daytons chemicals being sent to use on the foreign power in the form of the same poison gas that killed Dayton, Daytons business partners who will have Daytons share of the business come to them after Daytons death and the actual inventor of the chemical who has been cheated out of profits and recognition by Dayton.

Source: Wikipedia