Asathal is a Comedy Movie. Vetri(Satyaraj), Venu(Vadivelu) and Victor(Ramesh Khanna) are three friends, spending their time having fun. Of the three, Vetri is the rich one while the other two are simply taking advantage of his riches. For this reason, they do not want him to get married while his uncle(Manivannan) desperately tries to get him hitched.
A pregnant woman, on the run from a henchman, delivers her baby in Vetri's house and dies before revealing who the father is. Vetri announces in court that he is the baby's father but this lands him in more hot water than he had expected.