Colonel March is back in Paris and enjoying the company of Inspector Goron of the Surete at a bar.
While having a glass of Carcazon which seems off to Goron. He discusses with the Colonel their differing methods of detection.
Goron prefers to use the heart. The Colonel uses his head and prefers logic.
When a customer called Phillipe in the bar dies. It turns out that he was poisoned and he was also a monk as well a connoisseur of Carcazon.
The culprit might be Francois who was with Phillipe. It turns out that Francois was also a monk who came to Paris and fell in love.
Now Francois has returned to his remote monastery and taken a vow of silence. A monastery that makes Carcazon.
Goron meanwhile suspects the singer in the bar, the one who seemed close to Francois. Could it be a crime of passion?
An entertaining but a daft mystery. It made little sense, anyone could be a suspect and anything could be the motive. There is humour from Colonel March along the way.