Mercedes (Marga Lopez) dancings for cash with the customers of Salon Mexico, a famous cabaret in Mexico City. Her more youthful sibling Beatriz (Derbez) research studies in an expensive independent school, paid by Mercedes. Clearly, young Beatriz does not find out about her sis's work. Difficulties begin when Mercedes wins a danzon contest with Paco (Acosta), her pander. Paco rejects to share the prize with Mercedes, so she steals the money when he's sleeping.