Kamal Haasan, Sridevi, Silk Smitha
Lakshmi (Sridevi) a modern young girl, meets with an accident while returning from a party in a car and is hospitalised with severe head injuries. When she recovers, she is diagnosed with amnesia and she fails to recognise 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 brothel through devious methods. Srinivasan alias Cheenu (Kamal Haasan), comes to Chennai to meet his old friend (Y. G. Mahendran) and together, they visit the brothel to relax. The mistress sends Lakshmi, renamed as Vijaya, to his room. Cheenu realises 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 teacher. 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. Their relation however takes a turn when Viji accidentally spills ink over Cheenu' documents, angering him, but both eventually reconcile. Later, a local woodcutter lusts for Viji and nearly molests her, later she is saved. The sub-plot of the film follows the wife (Silk Smitha) of Cheenu' boss who is attracted to Cheenu, though Cheenu does not reciprocate her feelings.
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 neighbour. 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 travelling. He follows them to the railway station and tries to gain the attention of Viji, but she is unable to recognise him. Cheenu plays all her favourite 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 recognising him. Cheenu, who was hurt while chasing her car and trying to gain her attention, is left alone and limps away heartbroken.