A group of college students visit a beach and see the statue of a young lady with a shell in one hand and a lamp in the other hand. Their tourist guide narrates the story behind it.
In Echampakkam village, Perumooppan (A.K. Veerasamy), a fisherman and village head, finds a young child in an unmanned small boat and brings up the boy, Ponnan. A potter in the same village has a daughter who grows up to be a young girl Chelli (Poornima). Both Chelli and Ponnan (Vijayakanth) fall in love. Maari (Peelisivam) is obsessed with marrying Chelli as he is her muraimaman (maternal uncle).
At the village festival, Maari notices Ponnan and Chelli close together and warns Perumooppan about Ponnan's closeness to Chelli. One day when Ponnan and Chelli are together in the temple, the lamp breaks when someone throws a stone at it. The panchayat asks Chelli about her companion at the temple at that time and she does not reveal Ponnan's name. The panchayat punishes her by asking her to swim across the sea and bring mud to recreate the lamp. Chelli achieves it and the villagers are happy while Maari is unhappy.
Perumooppan sees the auspicious star in the sky and advises Ponnan and other fishermen to go for deep-sea fishing. While fishing, a shark takes away Ponnan. The fishermen return and inform Perumooppan and everyone believes Ponnan is dead. Chelli is shocked, tries to commit suicide, and gets saved by Maari. The villagers advise Chelli's father to get her married to Maari and the marriage takes place. While they return home after marriage, Chelli notices villagers carrying the dead body of a young child and gets upset and does not accept Maari's desire to consummate the marriage that night. Maari is upset and moves away and notices a tantric, Pillikoda (A. Jagadeesan) digging out the body of the buried child and chases him out. Perumoppan appoints Maari as one of the key members of the village panchayat.
When Maari and Chelli are together at the beach, Ponnan returns with a valampuri shell (a special one) and is shocked to see her married and leaves without meeting her. Understanding her situation he decides to be away from that village, to avoid any confusion in her life. For the last time, he visits Perumooppan's house and leaves the shell there. The next day, Perumooppan notices the shell and understands that Ponnan is alive as only he can retrieve such a precious shell from the deep sea. As days go by, Maari and Chelli start leading a normal life, and Chelli soon Chelli delivers a baby boy.
A rumour starts in the village that the child is dark looking and resembles Ponnan and Maari starts believing it. One day, when Maari goes to the temple, Pillikoda comes there and asks Maari to bring the first male child along with the valampuri shell kept at the Pampadevi temple in return for gold stones. Maari becomes greedy and decides to offer his child who is bringing him a bad name.
One night, Maari takes his child and the valampuri shell from the temple and goes to meet Pillikoda. Chelli wakes up, notices the child missing, goes to the Pampadevi temple, and prays to save the child. Meanwhile, Ponnan returns to Perumooppan and asks him not to inform anyone about him being alive. Chelli comes and informs Perumooppan about Maari taking away the child. She notices another valampuri shell (brought by Ponnan earlier) and Perumooppan advises her to keep it at the Pampadevi temple and pray for the safe return of the child. Perumooppan asks Ponnan to go and save the child.
Maari hands over the child to Pillikoda who tries to sacrifice the child in a Pooja. Maari reforms that time and seeks his child back but Pillikoda kills Maari in order to complete his Pooja. By then, Ponnan arrives, fights with Pillikoda, and almost kills him. Meanwhile, Chelli stands at the seashore with the valampuri shell in one hand and lamp on another hand praying to the deity for the safe return of her family. When Ponnan returns with the child and the dead Maari in a boat, Pillikoda throws a sickle killing Ponnan. The boat carrying the child alive arrives with both Ponnan and Maari dead and Perumooppan picks up the child. Chelli asks the sea deity about why her husband and her loved ones were affected and seek justice. Pillikoda is killed by the fire in the sea. Chelli continues to stay on the seashore. Her father makes a statue of her holding the lamp and shell in two hands and keeps it at the seashore.
[from the book Pride of Tamil Cinema: 1931 to 2013 by G Dhananjayan, Blue Ocean Publishers 2014]