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.