Bela Lugosi as Dr. Feodor Orloff / Prof. John Dearborn

Hugh Williams as Det. Insp. Larry Holt

Greta Gynt as Diana Stuart

Edmon Ryan as Lieutenant Patrick O'Reilly

Wilfred Walter as Blind Jake

Arthur E. Owen as Dumb Lou

Alexander Field as Fred Grogan

Gerald Pring as Henry Stuart

O.B. Clarence as Prof. John Dearborn (voice)

May Hallatt as Police Constable Griggs

Bryan Herbert as Police Sgt. Walsh

Charles Penrose as Morrison, undercover detective

Julie Suedo as Orloff's Secretary