In Vandalur, Chidambaram (T.S. Muthiah), a blacksmith is living with his daughter Anjalai (B.S. Saroja) and brother Kumaran (S.S. Rajendran). Chidambaram sends Kumaran to Madras for his college studies and works hard to send money for his stay there. He becomes seriously ill with tuberculosis and Kumaran learns of this. In order to relieve his brother's burden, he tries to move into a less expensive lodging. A public prosecutor (S.V. Ranga Rao) who instantly likes his good behavior offers a portion of his house for very less rent. To convince his wife, he states that Kumaran is married. However, his daughter Shanthi (Vijayakumari) finds out from Kumaran's diary that he is not married and starts liking him. Kumaran also falls in love with her and Shanthi's father and mother on knowing the truth that he is single give consent and decide to get them married.
Anjalai falls in love with Kasilingam (M.R. Radha), a ruffian with a blind sister Kumudam (Sowcar Janaki). Kasilingam also has a relationship with Mallika (Mohana) from Bangalore, who keeps sending money for his expenses every month, which he spends lavishly. Kasilingam's parents are worried about the wayward behaviour of him and also about their blind daughter, whom no one is willing to marry.
Chidambaram becomes seriously ill and Kumaran receives a telegram. He rushes with Shanthi and her parents. When Chidambaram comes to know that Kumaran is getting married to Shanthi and will be settling down in Chennai, he is worried about his daughter Anjalai and how much he thought about his brother's welfare and not the daughter's all along. That's when Kumaran accepts the responsibility to take care of Anjalai. Chidambaram takes a promise from Kumaran to protect Anjalai like his own daughter and then dies. Kumaran is unable to move to Chennai because of the promise.
One day, Kumaran finds out that Anjalai is in love with Kasilingam and he disapproves. But Anjalai requests and in order to fulfill his vow to his brother, he goes to meet Kasilingam's parents. They agree to the alliance, provided Kumaran gets married to their blind daughter Kumudam. Kumaran is shocked and finally agrees for Anjalai's sake.
Kumaran goes to Chennai and explains the situation to Shanthi and her parents. She is upset but accepts. Both marriages take place. Kumaran is disturbed about spoiling Shanthi's life and does not lead a happy life with Kumudam. One day Shanthi lands up at the village, sees the situation and makes Kumaran realize his mistake. Soon, Kumaran and Kumudam start living a happy life. Shanthi keeps visiting them regularly and Kumudam realizes that it is she, whom Kumaran sacrificed to marry her. Her respect for Shanthi goes up further. Kumaran takes Kumudam to Mahabalipuram for a holiday.
In the meanwhile, Kasilingam's lady love Mallika arrives from Bangalore and comes to know about his marriage with Anjalai. Kasilingam takes her to Mahabalipuram and tries to explain. Mallika shows his love letters and threatens to expose him. When he does not budge, she tries to kill him with a knife. He manages to overpower her, stabs her and throws her from the hilltop. Kumaran and Kumudam hear the cry and find the dead body of Mallika, and Kasilingam running away. He understands the truth and now is in a predicament, whether to expose Kasilingam or not? Because of his promise to take care of Anjalai, he takes the blame for the murder. Both Shanthi and Kumudam are shocked and plead with him but Kumaran is adamant and accepts the act of murder in the court.
The public prosecutor is Shanthi's father and Shanthi dons the robes to argue against her father. Step by step she dismantles the case against Kumaran. However, in the absence of any evidence, the court is yet to come to a conclusion. One night, in a drunken state, Kasilingam reveals that it was he who killed Mallika. Anjalai overhears this and to protect her innocent uncle, searches and locates the love letters of Mallika to Kasilingam and hands them over to Shanthi to fight the case. Shanthi shows them in Court, but they are not considered as evidence for the murder.
Kasilingam gets angry with Anjalai, beats her and dumps her in a temple, where he has hidden the dress he has worn during the killing and the knife used to kill Mallika. Anjalai finds them while appealing to the goddess. With great difficulty, she reaches the court and hands over the evidences. Kumudam also confirms that the person who stamped her feet while rushing out of the murder spot was none other than her brother Kasilingam. The court finds Kasilingam guilty. Realising the way everyone is working for truth and fairness including his wife, Kasilingam reforms and apologizes for his mistakes to Anjalai. Finally, Kumaran is acquitted and unites with Kumudam. Shanthi goes back to her life with her parents.
[from the book Pride of Tamil Cinema:1931 to 2013 by G Dhananjayan, Blue Ocean Publishers, 2014]