Imagi Ningthem (1981)

A teacher comes to a village and an old man asks her to tutor his grand son who is sickly all the time. The teacher becomes curious to know about the old man and the boy. She finds out from a colleague that the boy's mother had been seduced by a man and dies in child birth. It turns out that the father is husband of her cousin who is promptly apprised of the fact. Her cousin is attracted to the unfortunate boy and adopts him while her husband is absent. Subsequently the husband returns home and objects to the boy being adopted for he does not know it is his own son. The grand father wants to take the boy back but the step mother does not listen to it and ultimately keeps the boy.