The impossibility of guide her three daughters in life and the constant failed promise to be a good mother frustrate and imprison Susana more and more. Ana and Clara, her older daughters, decide to release her from her burden.
Every morning at school, when girls and boys stand in their lines, Sam, an alien boy, is confronted with his situation: he doesn't fit into this society where everything has to be classified. However, thanks to a teacher he will find his place in the world.
