Saravanan, orphaned by his dead mother – a mental patient, is adopted by a childless couple. Theirs is an inter-caste marriage. At college, he runs into Kavitha, the granddaughter of caste-obsessed Sengodan. The triangle is completed by Aavudayappan alias Armstrong, a US-return who is smitten by Kavitha.

With a little unintentional photo-swapping by the marriage broker, the parents of Saravanan and Aavudayappan (the fathers have the same name) both think they have an alliance for their son with Sengodan's family and show up at Kavitha's house at the same time. Romance flowers between Saravanan and Kavitha, who assume they are going to wed, while Aavudayappan continues to dream of Kavitha.

A series of contrivances allow this comedy of errors to carry on till the engagement where the announcement of the groom's name causes all sorts of confusions. Sengodan is now against the Saravanan-Kavitha union since Saravanan's parents are of different castes. Things come to a dramatic conclusion when Sengodan realises that Saravanan is indeed his own grandson, with a brief flashback relating to Boopathy  – Vasanthi marriage split due to her illness. The film ends with Saravanan and Kavitha marrying each other.