She was his first love, she was his illusion, she was his daydream. Until they taught him that she was his sin too.

The story runs in the 1940s Mexico City. A schoolboy (Carlos) falls in love with his best friend's mother (Mariana). Carlos is impressed because this family is not like the ordinary mexican families of the time, because they have many expensive American things, although they are not rich. The drama begins when Carlos gets out of school to go to declare his love to Mariana, and is discovered by his teachers.