Two Cistercian monks are brutally murdered near Lille; one of them was an old friend of commissar Niemans. Together with Camille Niemans engages in the investigation of the homicide, led by Sabrina Harel.

The investigation by Niemans and Camille revealed that the band BHP of the rock singer Messionier hides a group of extremely violent Satanists responsible for the murders of the two monks, the death of the mayor's young daughter and the disappeared girls.

In a chapel on the estate of the "God’s Grape Harvesters", a Christian sect in Rosheim, reverend Samuel Toschi apparently died in the restoration of the frescoes on the vaulted ceiling. While the local police have already stopped the investigation, as they assume an accident, commissar Niemans, who has travelled from Paris, has come to the conclusion that this is a homicide case.

Nieman's investigation indicates that the "God’s Grape Harvesters „consider themselves as God’s-chosen people who have always practiced inbreeding in order to preserve the purity of the blood and reproduce themselves in this way.

In Roubaix the severed hand of an unknown boy is found. Niemans and Camille are scheduled for the case. Locally, Niemans learns that three women were cruelly murdered in the village. Although local police authorities don’t want any interference in the investigation, Niemans makes additional inquiries on its own initiative.

Niemans and Camille convict the head of the youth welfare Michel Lagorce and the police officer Stéphane Gandolfi as perpetrators and accomplices of the murders in Roubaix. In the nineties, abused themselves in the children's home Saint Vincent, they lead, with the support of some children from the home, a campaign of revenge against those who were responsible.