 Scotland Yard is tasked with ensuring that the recently widowed Lady Gwendolyn Avon doesn t smuggle an expensive necklace known as Avon emeralds out of England. Most of her late husband s estate was given up in death taxes and the police are sure she could sell them at a premium abroad. Inspector Benson is tasked with ensuring the jewels  safekeeping but when they are stolen from the hotel safe, it appears Lady Avon has a perfect plan.