Begins with the exact same stock footage of London as The Avon Emeralds (1959), which aired just three weeks earlier.
This episode takes place in 1954.
Mr. Marriner tells Hewson that the "Murderer's Den" section of his wax museum must soon close as capital punishment will be abolished "any day now"; In fact, capital punishment was not abolished in the United Kingdom until 1967, thirteen years after the period of this story.
Hewson identifies one of the waxworks as "Petiot, Marcel", who was guillotined in 1946. This was a real case. Dr. Marcel Petiot was convicted of 26 murders, but was thought to be probably guilty of many more, perhaps over a hundred. Most of his victims were patients of his, desperately trying to escape the Nazis and accepting his apparent offer of help. Hewson also mentions another notorious French murderer as being depicted in the gallery - Henri Landru, the infamous bigamist, swindler and wife-killer executed by guillotine in 1921.