During the tour of variety stars Nelly & Sky, a guitarist dies, crushed by a spotlight. It was Sky who was targeted, as a second murder attempt quickly proves. To protect the star, Gréco imposes Beretta as guitarist for the next concerts. A big challenge for the inspector, who does not know if he will be able to improvise himself as a musician as his scales are rusty. Meanwhile, Rose discovers, horrified, that the murderer could very well be one of her patients. Indeed, Rico, a very psychologically disturbed musician, is convinced that Sky stole a song from him. Since then, he has sworn revenge.