In the Danish port city of Belgesund, the caretaker of a private high school has fallen victim to murder. Detective Thomsen takes on the case and finds that behind the clean facade there are abysses. He has five suspects in mind: the teacher Berling, who is having a relationship with a student, the twin brother and sole heir of the murdered man, the murdered man's shady roommate, the primary school teacher Klaus Erikson and his brother Jakob.