On November 17, 1901, Mexico City police raided a private party and arrested 41 men, half of whom were dressed as women. Clandestine transvestite balls were not unheard of at this time, and a raid would not normally gain national attention. However, Mexican cultural trends in literature, art, the sciences, and in journalism were inciting an atmosphere of sexual curiosity that was in search of the right turn of events to ignite a discursive explosion and focus interest on what was not a new phenomenon, but what was about to become a new concept: homosexuality. The editors treat the “nefarious” ball as a cultural event in itself and have assembled pictures, including the famous engravings by Posada, and have translated part of an historical novel about the event. At the same time, they uncover the underworld in Mexico City with essays on prison conditions, criminology, mental health discourse, and working class masculinities to create a rare and comprehensive slice of Mexican history at the turn of the century.