Lakshmi (Sridevi) a modern young girl, meets with an accident while returning from a party in a car and is hospitalized with severe head injuries. When she recovers, she is diagnosed with amnesia and she fails to recognize her own parents. She mentally regresses to the state of a child. While she is undergoing treatment, she is kidnapped and sold to the madam (Gandhimathi) of a whorehouse through devious methods. Srinivasan, also known as Cheenu (Kamal Haasan), comes to Chennai to meet his old friend (Y.G. Mahendran), and together, they visit a brothel to relax. The mistress sends Lakshmi, renamed as Vijaya to his room. Cheenu realizes that the call girl is still a child at heart and pities her. He understands that she is from a cultured family, was kidnapped and forced into prostitution. He returns the next day and after paying a huge sum to the mistress, takes her out in the pretext of a pleasure trip, then takes her away to Ooty, where he is working as a school headmaster. He takes her to his residence, where he protects her and also pampers her like a child. Viji, as she is called by Cheenu, has completely forgotten her past and becomes very close to him.
Viji's father Vedachalam (Veeraraghavan), who was searching her through the police, releases a newspaper advertisement about his lost daughter. A co-passenger who had travelled with Cheenu and Viji from Chennai to Ooty by train gives them a lead. Cheenu takes Viji to an Ayurvedic medical practitioner (Ramanamurthy) and leaves her there for treatment for a day. In his absence, the police come to his house searching for Lakshmi which he later learns from his sympathetic neighbor.
Finally, the police learn that Lakshmi is getting treated at the doctor's place and reach there. Cheenu is unable to come as he is afraid of police action. The treatment goes through successfully, Lakshmi regains her memory, becomes normal, and completely forgets about the period between her accident and recovery. Vedachalam and his wife are happy and decide to leave. From the doctor, Vedachalam learns that the person who had brought her there had been taking good care of their daughter; hence he withdraws his police complaint and they begin their journey to Chennai with Lakshmi.
After the police leave, Cheenu comes running after the car in which Viji (Lakshmi) is traveling. He follows them to the railway station and tries to gain the attention of Viji, but she is unable to recognize him. Cheenu plays all her favorite pranks, but Viji (Lakshmi), unable to comprehend, thinks that he is mentally challenged and begging for food. Cheenu continues his fruitless attempts to gain her attention. Finally, the train leaves with Viji not recognizing him. Cheenu, who was hurt while chasing her car and trying to gain her attention, is left alone and limps away like a heartbroken child.
[from the book Pride of Tamil Cinema: 1931 to 2013 by G Dhananjayan, Blue Ocean Publishers, 2014]