Studer investigates a double murder in Bern and Basel. Two Swiss women have been killed by gas leaks, murders thinly disguised as accidents. The stalwart sergeant encounters a pretty young woman, a strange monk and tales of a geologist dead from a tropical fever in a Moroccan Foreign Legion post as he stumbles onto a murky oil deal involving rapacious politicians and their henchmen. With the help of a hashish-induced dream and the common sense of his stay-at-home wife, Studer solves the multiple riddles and leads the investigation to a typically Glauserian end.