'What if he'd done it in reverse? Supposing the murder had already been committed by the time you saw him?' The elegant actress Tessa Crichton is starring in a film to be made in Paris.
Her husband Robin (otherwise Detective Inspector Price of Scotland Yard) and her cousin Ellen travel with her but the trip is off to a peculiar start when Tessa's jewel case disappears - and mysteriously turns up again; no jewellery missing.
She and Robin go racing at Longchamps, attend an eveni.