Mercedes (Marga Lopez) dances for cash with the customers of Beauty salon Mexico, a well-known cabaret in Mexico City. Her more youthful sis Beatriz (Derbez) studies in a costly private school, paid by Mercedes. Undoubtedly, young Beatriz doesn't understand about her sis's work. Difficulties begin when Mercedes wins a danzon competition with Paco (Acosta), her pimp. Paco declines to share the prize with Mercedes, so she takes the money when he's sleeping.