It is springtime in idyllic St Denis, a time of beauty and calm. But not for Bruno, Chief of Police: a woman's body has been found on a boat, bearing signs of a black magic ritual. Bruno has much on his plate—a domestic abuse case that needs careful handling and a dodgy local development proposal that seems too good to be true. But a murder case must take precedence, and the roots of this one lie buried deep in the past, leading Bruno to a chateau above a bend in the river to the reclusive old woman who lives there and the secret hidden in the Devil's Cave.