Sherlock Holmes

Doctor Watson

Nancy Partridge

William Easter

Heinrich Hinckel aka Richard Stanley

Naval Lt. Pete Merriam

Mr. Lang, government agent

Detective Lt. Grogan

Howe

Mrs. Hudson

Cady

George

Mrs. Pettibone

Mr. Ahrens

Sen. Henry Babcock

Antiques Store Sales Clerk

Army Inspector (uncredited)

Alfred Pettibone

Sir Henry Marchmont (uncredited)

Miss Pringle (uncredited)

Party Pianist (uncredited)

Hotel Doorman (uncredited)

Mrs. Ruxton