It is the female detective, Lady Molly of the Yard created by written by Baroness Orczy.
When a customer slumps in a Viennese cafe, dead after drinking some hot chocolate, Lady Molly's assistant Mary Grandard (Ann Beach) was nearby.
The dead man Mark Culledon was from a society family and a woman of Austrian origins is held as a suspect. A woman with a big hat was seen with the victim near the time of his death.
Culledon's aunt who dotted on Mark is distant and even irritated with Lady Molly (Elvi Hale) and her investigation. There is something Lady Molly is uncertain about, why would a woman wear a hat that is so big. It points to someone being fitted up for the murder.
It is unusual to see a female detective, Lady Molly was created in 1910. She is seen investigating with Inspector Saunders (Peter Bowles) who is exasperated with some of her methods which could invite trouble such as the ad in the paper offering a reward for information.
There is a side plot of some lower class parlour maids doing some shoplifting who are linked to the Culledons.
It is a layered mystery, the character of the newly married Mark Culledon is ripped apart, someone who was rather cruel and callous which hints why someone would want him dead.
Lady Molly is clearly clever, she solves the mystery using a woman's intuition. It is just a shame that the drama as depicted was a tad dry. It is all so talky which makes the drama stilted, it looks so much like a stage play even though there were a few sly lines here and there. I think a lot of it was due to this being a studio bound production.
Elvi Hale tries to add zest to her character, she is ably supported by her assistant Mary Grandard who actually gives the clue to the mystery early enough. It is just a shame that the direction of this episode was so uninspired.