The Devil's Cave: A Mystery of the French Countryside / Walker, Martin

The sixth installment in the delightful, internationally acclaimed series featuring Chief of Police Bruno.

It's spring in St. Denis. The village choir is preparing for its Easter concert, the wildflowers are blooming, and among the lazy whorls of the river a dead woman is found floating in a boat. This means another case for Bruno, the town’s cherished chief of police.
 
With the discovery of sinister markings and black candles near the body, it seems to Bruno that the occult might be involved. And as questions mount—most notably about a troubling real estate proposal in the region and the sudden reappearance of an elderly countess—Bruno and his colleagues are drawn ever closer to a climactic showdown in the Gouffre de Colombac: the place locals call the Devil’s Cave.