Periya Idathu Pen, Murugappan (M.G.R.) is a simple village youth, living with his widowed sister, Gangamma. He wishes to marry his master’s daughter Tillai, but the village head Pillai’s son Sabapathy, plays foul with the help of his sister Punitha (Saroja Devi) and weds her. Murugappan learns of this and vows to marry Punitha a very proud and head strong girl and teach her a lesson.Unable to tolerate Murugappan’s democratic ways, Pillai torches their hut and forces himself on Gangamma. Murugappan is forced to leave the village and go to the city to make a living. Does Murugappan succeed in his mission? Does Gangamma get Justice?