Juan Carlos Thorry is a police inspector who must solve the mystery of the death of the warden of a boarding school for young women, for which he goes undercover as a music teacher. The main suspect is the mischievous schoolgirl María Duval. A series of entanglements leads the protagonists to becoming romantically involved and to finding the culprit.
A Young man from a wealthy family hide them his attraction for tango culture of arrabal. In a milonga he fell in love with Mirella and he have a knife fight with all others guapos that want her, he won. Time pass and Mirella became a mistress but this situation is unstable because of the society prejudices.