The Plot Thickens

James Gleason

Police Insp. Oscar Piper

Zasu Pitts

Hildegarde Withers

Owen Davis Jr.

Robert Wilkins

Louise Latimer

Alice Stevens

Arthur Aylesworth

Kendall

Paul Fix

Joe

Richard Tucker

John Carter

Barbara Barondess

Marie

James Donlan

Jim

Agnes Anderson

Dagmar

Oscar Apfel

Robbins

Alyce Ardell

Josephine, Hildegarde's Maid (uncredited)

John T. Bambury

Midget (uncredited)

Billy Dooley

Gas Station Attendant (uncredited)

Frank Fanning

Detective Fanning (uncredited)

Mary Gordon

Woman with Bag (uncredited)

Reed Howes

Museum Guard in Egyptian Room (uncredited)

John Indrisano

Man in Line for Inspection (uncredited)

Lew Kelly

Cassidy, a Policeman (uncredited)

John Miltern

Mr. Gordon, Museum Guard (uncredited)