Inspector Matthai discovers the horrific murder of an eight-year-old girl. When he tells the girl's mother, she makes him swear on his soul to find the killer - and so begins Matthai's obsession with the case and the dark world beneath the polite veneer of 1950s Swiss society.

Written by Friedrich Durrenmatt and dramatised for radio by Steve Chambers, this story was also adapted into a film in 2001, directed by Sean Penn and starring Jack Nicholson.