"Kruso" tells of the last summer before the Wall came down on the small island of Hiddensee in the Baltic Sea. Beyond state-organized tourism, the isolated island became a kind of artist colony every year and a place of longing for dropouts and alternatives. Due to its proximity to Denmark, Hiddensee was also the starting point for the flight across the Baltic Sea.

Policeman Koops witnesses a car accident. The dying driver gives him an envelope with the part of a code. Shortly thereafter, Koops gets in the sights of a contract killer.

While drinking coffee at an outdoor café, Dupin sees a man drop to his death.

At the bottom of a lake, the police find a car with a wax corpse in the trunk. It is 15-year-old boarding school student Alex, who has been missing for five years. With the sad certainty that she has been murdered, the case, which should have been closed, takes a completely new turn. Her teacher, the charismatic Hajo Rick, convicted of her murder on the basis of circumstantial evidence and witness statements, could be innocent after all! When the ambitious defence lawyer Sophia Dreyer obtains a retrial, the former investigator finds himself in trouble: Chief Inspector Kai Matzen now has to throw the certainties of the past overboard - and realize that he is more personally involved than he would like. Sophia also suspects that she can't trust anyone. And what if it was Hajo Rick after all? Dreyer and Matzen investigate independently of each other, each in their own interest, and reconstruct Alex's last hours. In the process, they uncover an intrigue.