"The surprise witness ! The searching question ! The perjured testimony ! The accusing finger ! The shattering truth !"
A California commercial pilot sees a telecast in London of an interview with Sir Mark Lodden at his home. The Canadian is convinced that the baronet is a fraud, and he is actually a look-alike actor named Frank Welney.
Sir Mark Loddon / Frank Welney / Number Fifteen

Lady Margaret Anne Loddon

Jeffrey Buckenham

Sir Wilfred

Hubert Foxley

Gerald Loddon

The Judge

Himself

Dr. Schrott

Maisie

Associate

Editor
The Guide

Admiral Loddon

Michael Loddon

The Butler

First Photographer

Second Photographer

Maddox
Car Salesman

Miss Sykes

Mrs. Squire

Fitch

Barmaid
Man at Bar
Girl in Street

Barrister (uncredited)
Newspaper Vendor (uncredited)

Barrister (uncredited)