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

Plot
Simon Dayton is in fear for his life and seeks the help of Mr. Wong to protect him. Just prior to meeting Mr. Wong, Dayton is found dead in his office without a mark on him with several witnesses testifying Dayton was alone in his office that was locked from the inside. Though the police view Dayton’s death as due to a heart attack, Mr. Wong discovers a broken glass ball that contained poison gas.

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

Cast
Boris Karloff as Mr. James Lee Wong
Grant Withers as Captain Sam Street
Maxine Jennings as Myra Ross, Dayton’s Secretary
Evelyn Brent as Olga Petroff / Countess Dubois / Sophie Dome
George Lloyd as Detective Lt. Devlin
Lucien Prival as Anton Mohl, aka Baron Von Krantz
John St. Polis as Carl Roemer, Poison Gas Inventor
William Gould as Theodore Meisel, Dayton’s Partner
Hooper Atchley as Christian Wilk, Dayton’s Partner
John Hamilton as Simon Dayton, President Dayton Chemical Co.
Wilbur Mack as Russell, Dayton’s Office Manager
Lee Tung Foo as Tchin, Wong’s Servant (credited as Lee Tong Foo)
Lynton Brent as Detective Tommy