While the Patient Slept

Aline MacMahon

Nurse Sarah Keate

Guy Kibbee

Detective Lt. Lance O'Leary

Patricia Ellis

March Federie, Richard's Granddaughter

Hobart Cavanaugh

Eustace Federie

Dorothy Tree

Mittie Federie

Robert Barrat

Adolphe Federie

Helen Flint

Isobel Federie - Adolphe's Wife

Lyle Talbot

Ross Lonergan

Henry O'Neill

Elihu Dimuck

Walter Walker

Richard Federie

Allen Jenkins

Police Sgt. Jim Jackson

Eddie Shubert

Detective Muldoon

Russell Hicks

Dr. Jay

Brandon Hurst

Grondal - the Butler

Joseph E. Bernard

'Murph' Murphy - the Ballistics Expert (uncredited)

George Chandler

Evening Bulletin Reporter (uncredited)

Nick Copeland

Detective Davis aka Johnson (uncredited)

Joseph Crehan

Evening Bulletin Editor (uncredited)

Bill Elliott

Bank Teller (uncredited)

Virginia Howell

Kema - the Cook (uncredited)