Sherlock Holmes in Washington

George Zucco

Heinrich Hinckel aka Richard Stanley

John Archer

Naval Lt. Pete Merriam

Gavin Muir

Mr. Lang, government agent

Edmund MacDonald

Detective Lt. Grogan

Don Terry

Howe

Mary Gordon

Mrs. Hudson

Bradley Page

Cady

Clarence Muse

George

Mary Forbes

Mrs. Pettibone

Holmes Herbert

Mr. Ahrens

Thurston Hall

Sen. Henry Babcock

Ian Wolfe

Antiques Store Sales Clerk

John Burton

Army Inspector (uncredited)

Gerald Hamer

Alfred Pettibone

Gilbert Emery

Sir Henry Marchmont (uncredited)

Margaret Seddon

Miss Pringle (uncredited)