Neengal Kettavai(1984)

Original title: நீங்கள் கேட்டவை

Poornima, a widow living in Ooty leads a peaceful life with her two sons. Jaishankar, a tourist who visits the place gets tempted and rapes her. In the act, Poornima dies leaving her two sons who witness the murder. With a turn of events leading to both sons joining together and take revenge for their mother's death forms the rest of the story.