Cnut - Cabal of Silence

Open season on legal eagles. A corpse dumped in Politimester Alex Skanvik's boathouse is enough to give Cnut indigestion, when he is disturbed at his breakfast by a phone call from his boss, but he has no inkling that the corpse will bring him one of the strangest cases he has ever investigated. The dead man was a lawyer, and at autopsy, Viv Blenke, the pathologist, discovers that his scrotum has been cut, as if the killer intended castration, but did not continue with it for some reason.
The following morning, another lawyer is found dead by the water's edge, and again the scrotum has been cut. Both men went to university together, 16 years earlier, but there seems no reason why they were selected to die, or why their bodies have been left beside water, unless it has to do with the party held at the end of the university course that both men attended. That party was at the Devil's Grotto.
Men are not the only targets of the killer, and the next victim is a woman, found at that location, and the cut on the genitalia is there again. Cnut and Ilse begin to believe that the killer is selecting victims at random from the list of ex-students, and is killing them in revenge for the disappearance of either Benni Bensen or Bente Enders, both of whom went entirely off the radar the day after that course ended.
It seems possible that one or both of them may have died at the party. The detectives are stymied by the reason for the cuts to the sexual organs, but the big question is, why wait sixteen years for revenge? It is obvious that that killer is one of the men or women who were on that university course, but the questioning of all of them produces nothing except another death, at the hands of a different killer.
The action then accelerates to an incredibly twisted and dangerous ending - one that no one could have possibly foreseen.