The Boxer Germán Bronco Torres loses his license, and works as bouncer at the cabaret El Pirulí, where he falls for the fichera Carmen, and befriends of the pimp Margarito Fuensanta El Vaselinas, who lost a bet and has to pay to a gangsters. For 500 pesos for El Vaselinas, Bronco prepares a trap in the cabaret to the taxi driver Raul, to seduce his girlfriend, not knowing that the victim is his own sister Lupita.