Sinopsis

Dürrenmatt uses a first-person narrative to insert himself into a frame story as a writer of detective fiction. However, the primary narrator is actually a character named Dr. H., a retired police chief who takes on the role of explaining to Dürrenmatt's first-person character the flaws of the detective literature genre. To do so, Dr. H. relates the story of one of his former inspectors, Matthäi, who on his last day with the department, found himself called into an investigation of child murder. A suspect soon confessed to the crime, but knowing that the confession came only after the man was browbeaten in a relentless, 20-hour interrogation, Matthäi's keen police instincts told him that the man was not the real murderer. Matthäi felt that there was a serial killer at work, with the girl's murder being related to other child murders that had occurred in the surrounding cantons. However, he was alone in that assessment and the police closed the case.

Having made a solemn promise to the parents of the murdered girl that he would find the culprit, Matthäi abandoned the plans he had made for his life in retirement and instead continued investigating the case as a private citizen. He was warned by a psychiatrist that the murderer he sought likely did not exist and thus he might drive himself mad with his obsession in finding the man. Matthäi, however, was undeterred.