Rex and Terzani find themselves catapulted into the world of struggling singles. Antonio Tassinari, known professionally as Excel - a renowned seduction instructor who conducts courses teaching shy men how to overcome their inhibitions- is stabbed to death in a lounge bar while carrying out a "practical lesson". Terzani follows various leads that introduce him to the milieu of Master Mind, the ultimate guru for timid would-be seducers. The victim appears to have been killed by one of his numerous female conquests, but all of the possible traces are dead-ends. But the inspectors soon discover he had been trying to break into another industry.

A senior post office official is murdered in his flat. Terzani and Rex's investigations seem to point to the victim's ex-wife, who has never resigned herself to her husband's separation. So many clues seem to lead to her that Gori decides to detain her for further questioning. Terzani and Rex, however, discover that the situation is much more complex and dangerous, as they find themselves on the track of a mysterious dismantled atomic bomb which a gang of Chinese criminals are smuggling through Italy. Having succeeded in intercepting some components of the bomb, the inspector and Rex are still hunting the final piece, containing the plutonium necessary to detonate the device, in Rome's Fiumicino Airport.

An undercover policeman, Michele Rossi, infiltrated in a major criminal organisation, is ambushed and killed by two mysterious professional killers. Inspector Terzani, a close friend of the victim, disobeys Gori's orders and conducts his own investigation. In incognito, Terzani and Rex get themselves admitted as patients in a luxurious private clinic run by an important specialist, Dr. Nevio Cangelosi.

While Terzani, Rex and Monterosso are enjoying themselves at the 'Magicland' amusement park, a dancer named Marie who performs in one of the shows is found murdered. The investigations focus on the professional rivalries and jealousies between assorted dancers and stunt men, and then on Massimo Forghieri, the park's director, whom Terzani and Rex discover runs a thriving illegal amphetamine trade among his employees. But the solution to the murder case is far more complex and contorted, and has its roots in a series of tragic events in the past which continue to cause bloodshed in the present.

An irresistibly attractive tango teacher, Corrado Fanti, is found murdered in his tango school. He has been poisoned, and his home ransacked in search of something. The investigations concentrate on the tensions and romances surrounding the handsome teacher's relations with his female students, perpetually competing for the privilege of dancing - and more - with him. While investigating, Terzani and Rex discover that the school's female tango teacher is being targeted by the same killer.

A female teacher taking part in a school outing to Rome comes to the police station to report that one of her students, Sara Borelli, has been bullied and drugged while she was in the hotel. Interrogated by Terzani, Sara recounts how she had been unwittingly drugged by classmate Clara Moretti. But then Clara's dead body is found just near the police station, having fallen from the bathroom window of her hotel room. What at first had seemed a tragic accident soon turns out to be a case of murder among classmates - and possibly a teacher. But the terrible truth will require all Rex's skills and intelligence before it is finally revealed.

Terzani and Rex investigate when the wealthy owner of a construction company is killed by a rifle shot during a hunting party.

When the president of a chocolate factory, Ruggiero Onorati, dies from eating a poisoned chocolate, Terzani and Rex focus their investigation on the man's family, where various bitter conflicts come to light. The victim's sister, Giulia Onorati, had angrily fallen out with him over company strategy concerning the family chocolate business. However, the investigations are turned upside down when an epidemic of botulinus poisoning - a toxin contained in a batch of chocolate snack biscuits produced by the victim's company - hits Rome.

The president of a rugby club, Eugenio Sartor, is killed in his home shortly after watching a team training session. Sartor, the owner of the Eagles, had been forced to seek help from his brother-in-law Mazzilli to put the club's finances in order. Mazzilli had thus become the victim's business partner, relinquishing his ownership of a second division football club. Terzani and Rex are initially suspicious of one of the players, Michele Caccia, and then of a criminal implicated in a football match-fixing scandal, Merlo. The latter, however, is shot dead by Mazzilli while trying to kidnap Sartor's daughter. Terzani and Rex have a lot to untangle, between family conflicts, match-fixing and money laundering.

A professor from an online university is found murdered in a suburb of Rome. The investigations focus on the university, and Inspector Terzani and Rex explore the variegated world of the online Faculty, which has bases in Rome, Novedrate and Messina. The professor had taught cultural anthropology, and it is this discipline which puts the inspector on the track of a mysterious spiritual community which the professor had suggested as the subject of a graduation thesis on the method of "participating observation".