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.

Shortages in postwar Berlin have created a blooming black market, and the goods rounded up during a major police raid all seem to come from the same source. The trail leads Commissioner Naumann to the Alibaba Cabarett, but he is unable to find conclusive evidence to convict its owner Goll.

Whodunit centered around a hostel.