A serial killer who specialises in killing teachers is on the loose and Andrea becomes accidentally involved when he decides to lend a hand to one of the victims and catches a glimpse of the nocturnal predator.

Madonna Violante goes to Rome to find the three Armida daughters, Lorenza and Vanna, who she has not seen for many years; but first she stops by her friend Antonia from whom he learned many unseemly things about them.