massa and mahavir's wife deliver their babies at the same time when both their husbands are away. Massa's baby is stillborn and her co-sister is about to die post delivery (since she fell down the stairs before getting pain). She gives her baby to massa and asks her to bring up the baby as her own son and takes her vow that she will not reveal it to anyone as she does not want her son to be brought up as Mahavir's son. Then she dies. Only the mid-wife knew about it and now she reveals it to Mahavir when she comes to ask his favor to return her son's land. After all this drama, Basant who has come to know of the truth refuses to accept Mahavir as his father. After regular cliched drama, Mahavir turns into a new leaf, returns all the land that he had grabbed from villagers, brings Anandi's father from jail (he was frammed for possesing illegl weapons as per Mahavir's plan), accepts all his crime and goes to jail. Basant wants to leave but massa insists that he is her eldest son and would remain so till her last.
hope this helps.