Madame Mistério

William Powell

Dr. Lawrence 'Brad' Bradford

Jean Arthur

Paula Bradford

James Gleason

Inspector Corrigan

Eric Blore

Stokes, Bradford's Butler

Robert Armstrong

Nick Martel, Bookie

Lila Lee

Miss Prentiss, Bradford's Receptionist

Grant Mitchell

John Summers, Luxury's Owner

Erin O'Brien-Moore

Mrs. Summers

Ralph Morgan

Leroy Hutchins, War Cloud's Owner

Lucile Gleason

Mrs. Hutchins

Johnny Arthur

Mr. Frankenstein (uncredited)

Stanley Blystone

Police Radio Operator (uncredited)

Tom Brower

Police Sergeant (uncredited)

Spencer Charters

Dr. Bunting (uncredited)

Frankie Darro

Spike Salisbury (uncredited)

John Dilson

Analyst Examining Gelatin Capsule (uncredited)