The Mystery of Mr. Wong is a 1939 American mystery film directed by William Nigh and starring Boris Karloff.

Plot
The second in the series of Mr. Wong features starring Boris Karloff finds wealthy gem-collector Brandon Edwards gaining possession of the largest star sapphire in the world, the ‘Eye of the Daughter of the Moon’, after it has been stolen in China. Edwards, at a party in his home, confides to Mr. Wong that his life is in danger. During a game of Charades, Edwards is mysteriously shot dead and the gem disappears. Unknown to Wong, the jewel is in the possession of Edwards’ maid, Drina, who intends to return it to China, but she is murdered also, and the gem is taken again. After one more murder—the suspect list is dwindling—Wong exposes the killer, turns him over to Police Inspector Street, and Wong orders his manservant Willy to return the gem to China.

Cast
Boris Karloff as James Lee Wong
Grant Withers as Police Captain Sam Street
Dorothy Tree as Valerie Edwards
Craig Reynolds as Peter Harrison
Ivan Lebedeff as Michael Strogonoff
Holmes Herbert as Prof. Ed Janney
Morgan Wallace as Brandon Edwards
Lotus Long as Drina, the Maid
Chester Gan as Sing, the Butler
Hooper Atchley as Carslake
Bruce Wong as Asian Man
Jack Kennedy as Policeman
Joe Devlin as George, the Detective
Lee Tung Foo as Willie (as Lee Tong Foo), Wong’s Butler and door opener.
Wilbur Mack as Ballistics Expert
Dick Morehead as police detective
I. Stanford Jolley as Charades Player (uncredited)