Saraswathi "Yamuna", the younger daughter of an Orthodox father, comes to Madras for finishing her studies. Major Madhavan, the husband of Yamuna's elder sister Ganga, gets infatuated with Yamuna after seeing her photo in a letter sent by her. Meanwhile, Yamuna meets Jeevanantham "Jeeva" in a bus, who gives his ticket to her as she had not taken her own. Later one day, Jeeva decides to express his love to Yamuna by writing "1 4 3" (the number of letters in "I love you") in a letter and giving it to her, but he witnesses a group beating a boy who did the same thing, so he disposes the letter. It is found by Yamuna, who realises his love.