On the night that she was killed, Irene played her final concert. First violin in an orchestra and the daughter of Adele Rubini, the owner of a prestigious theatre, she was a talented and beautiful young woman.

A university math professor, Emanuele Sarti, is found dead in a tunnel inhabited by a homeless man in Valentino Park. Strange mathematical formulas are discovered written on the walls of the tunnel: improbable that it's a coincidence.