Jan Euler is a young investigator who is trusted with the most complex cases. It is he who is tasked with investigating the death of a wealthy heiress and her three friends in a quiet holiday village. At first glance, it seems that a maniac has gotten to the girls, but Ian is in no hurry to draw conclusions; he quickly finds out that each of the victims had enough dark secrets in their past. A deal with the mafia, an attempt to steal someone else’s husband, an affair with a sadist - what ultimately led to a bloody massacre? It seems that the answer is already close, but the main tragedy of his life is unexpectedly used against Ian - the murder of his twin sister, which remains unsolved. Now he has to not only get on the trail of the elusive criminal, but also figure out who knows so much about his past and is manipulating his present.