Walter Cherubini, in the middle of the night, receives a mysterious phone call in the editorial office. This is the widow Mazzanti, admitted to a famous private clinic in Parma, who claims to be held prisoner. The next day, the opera singer Marinelli, also a guest at the facility, was found dead. The reporter, having infiltrated the clinic and aided in the investigation by a nurse, will be able to unravel the mystery.