Stanley Ridges as Prof. George Kingsley / Red Cannon

Boris Karloff as Dr. Ernest Sovac

Bela Lugosi as Eric Marnay

Anne Nagel as Sunny Rogers

Anne Gwynne as Jean Sovac

Virginia Brissac as Mrs. Margaret Kingsley

Edmund MacDonald as Frank Miller

Paul Fix as William Kane

Murray Alper as Bellhop

Jack Mulhall as Bartender

Raymond Bailey as Louis Devore

Joe King as Chief of Police

John Kelly as Taxi Driver

Jessie Arnold as Nurse

Elfriede Borodin as 2nd Nurse

Tommy Conlon as Student

Franco Corsaro as Club Maitre d' (uncredited)

James Craig as Reporter Ernst Gives Notes To

Kernan Cripps as Detective

Eddie Dunn as Det. Farnow

Edward Earle as Detective

Harry Hayden as Prison Doctor

Frank Jaquet as Fat Man in Bar

Ellen Lowe as Midtown Hotel Maid

Jerry Marlowe as Midtown Hotel Clerk

Jerry Marlowe as Cabbie

Wallace Reid Jr. as Student

William Ruhl as G-Man

Frank Sheridan as Prison Chaplain

Edwin Stanley as Dr. Warner

Harry Tenbrook as Cabbie

Emmett Vogan as Det. Carpenter

Russell Wade as Student

Dave Willock as Student

Victor Zimmerman as G-Man

Robert Morgan as Hotel Associate