Mr. Wong, Detective

Boris Karloff

James Lee Wong

Grant Withers

Police Capt. Sam Street

Maxine Jennings

Myra Ross

Evelyn Brent

Olga Petroff / Countess Dubois / Sophie Dome

George Lloyd

Devlin

Lucien Prival

Anton Mohl

John St. Polis

Carl Roemer

William Gould

Theodore Meisle

Hooper Atchley

Christian Wilk

John Hamilton

Simon Dayton

Wilbur Mack

Russell

Lee Tung Foo

Tchin

Lynton Brent

Tommy

Grace Wood

Mrs. Roemer

Frank Bruno

Lescardi (uncredited)

Ed Cassidy

Ambulance Doctor (uncredited)

Wheaton Chambers

Chemistry Lab Director (uncredited)

Clancy Cooper

Warehouse Man (uncredited)

George DeNormand

John (uncredited)

Lester Dorr

Coroner (uncredited)