A quarrel between divorced waitress Mája () and her fifteen-year-old son Petr () ends with the boy physically attacking his mother, and he is sent to an institution for juvenile delinquents. Over three years Petr successfully trains and qualifies as a carpenter, but consistently refuses to see his mother. Nonetheless, the experienced director Janes () hopes that Petr will manage to make a new life for himself with his mother. Petr is now of age and returns to Prague.