 Mercedes (Marga Lopez) dances for money with the clients of Salon Mexico, a famous cabaret in Mexico City. Her younger sister Beatriz (Derbez) studies in an expensive private school, paid by Mercedes. Obviously, young Beatriz doesn t know about her sister s job. Troubles begin when Mercedes wins a danzon contest with Paco (Acosta), her pimp. Paco refuses to share the prize with Mercedes, so she steals the money when he s sleeping.