This book tells a story that took place in a small space over a very long time, and that has as 'main characters' two cities linked by a destiny rooted in the myth and image of the shewolf. The space is the one occupied today by the church and oratory of St. Catherine of Siena in Via Giulia in Rome; the time is that which elapsed from the germinal idea of reserving a sacred building just for people from Siena living in Rome (the so-called 'Nazione Senese') to the construction of the present structures; in other words, from the late Middle Ages to the end of the 18th century.