Synopsis Trevor?
The film is based on the book of the same name by French author Jean Christophe Grange and involves a weird murder which takes place in a Northern French university town. A detective is sent there to investigate and at the same time, a younger cop is investigating the violation of a mausoleum in his town: his investigation leads him to the same town and he joins forces with him to expose the murderer.
I should add that this movie - while actually a cop thriller - has many horrific images such as this:
Dominique Sanda as the blind, insane nun