Pillai Kaniamudhe is the story of Ranganathan who lost his pregnant wife to the disaster of Tsunami. Later he got married to Rukmini, who unfortunately not blessed with child birth. Hence they plan to adopt a child from an orphanage and do so. Later on Ranganathan comes to know from the records of the orphanage that the child he adopted is his own! The child along with the mother got admitted in the orphanage after the Tsunami. After handing over the child to the trustees, the mother passed away.
Thus Ranganathan gets his own child back and his second wife is also happy that she is the present mother for her husband's child!