Mercedes (Marga Lopez) dances for money with the clients of Beauty salon Mexico, a well-known cabaret in Mexico City. Her younger sis Beatriz (Derbez) researches in a pricey independent school, paid by Mercedes. Obviously, young Beatriz does not find out about her sister's work. Difficulties start when Mercedes wins a danzon contest with Paco (Acosta), her pimp. Paco declines to share the reward with Mercedes, so she steals the money when he's resting.