Out of his jurisdiction and not a local, Dupin needs to work with his equivalent Commissaire to understand the history and value of the salt industries and the implications of what four plastic blue barrels, left on the edge of a pool could mean.
I learnt about the salt industry and its importance (historically and economically), the local area and its myths and legends of its past. The writing was tight and moved at a good pace. 
I am already looking forward to reading more of this author – there are lots to choose from 😊  

Other titles by the same author:
An island of suspects (2025!!)
Death of a master chief # 9 (2024)
The body by the sea # 8 (2023)
The King Arthur case #7 (2022)  - see my review of this book 
The granite coast murders # 6 (2021) 
The killing tide - # 5 (2020) 
The missing corpse #4 (2019) 
Murder on Brittany Shores #2 (2016)
Death in Pont Aven #1 (2014)