 Set in the rich and luxurious Monte Carlo, one day, Dee-Jay Jean Loup Verdier, while transmitting on the radio, gets a delirious phone call. The person on the other end of the line, with an artificial voice, declares that he is a murderer. The phone call is dismissed as a stupid game, but the next day a Formula One pilot and his girlfriend are found dead and horribly mutilated. This cruel double murder shakes the city, which has always been a safe place. The investigation is assigned to detective Hulot, whose family situation is very troubled. In fact, after the premature death of his young son, Hulot s wife starts pretending that their son is still alive. Hulot is a very sympathetic detective and he is an old friend of FBI agent Frank Ottobre; together they will do their best to discover the murderer. During their investigation, the killer strikes again. Information-technology millionaire genius Allen Yoshida, who created an operating system that competes with Microsoft, is found drained and horribly mutilated in an underground garage. Other murders will follow. Every one of them is pre-announced by a phone call and a leitmotif that leads to the next victim. A peculiarity of these killings is that all the bodies are mutilated and their faces are taken away to make a mask. The two detectives, who are trying to solve this puzzle, in a city that is not accustomed to violence and cannot accept it, meet many incredibly moving characters, such as Pierrot, a young boy with downs syndrome, who is a sort of human computer and idiot savant, and, with his surprising expertise in music, he helps Hulot and Ottobre to solve the enigma.