Edgar Lustgarten explains the modus operandi of certain criminals. How not deviating from it can ultimately lead to them being caught.
In the Strange Case of Blondie, departing from the modus operandi lead to their capture.
A series of burglaries has common themes. A young lady would visit an expensive house posing as a market researcher. It allowed them to case the joint.
Later that night she would return to steal. This time, she was disturbed and hit the owner of the house hard on the head. He later died.
The blonde was described as slim and aged 25 years. There is a comical scene as the police apprehend all young blonde women.
Inspector Harmer looks for patterns and sees that the Blondie started the burglaries in London and moved outwards to Liverpool, Manchester and Newcastle. Then back towards London.
It brings them into contact with music hall performers who have been taking a similar route to the thefts.
There were too many scenes where the description of the suspect is constantly being repeated by the police. Maybe it was meant to disguise the twist and let it come as a shock.
It was shocking, there was no way she was 25!