Thenali (Kamal Hassan) is a man who fears anything and everything due to his earlier life in Sri Lanka. Dr. Panchabhootham (Delhi Ganesh) and his assistant (Ramesh Khanna), who are the doctors treating Thenali, are jealous of a relatively junior doctor Dr. Kailash (Jayaram) getting all the media attention. They send Thenali to Dr. Kailash because the former will make people mad because of his antics and expected him to do the same on Dr.Kailash, who is on a vacation to his home in Kodaikanal where his wife Jalaja(Devayani) and two children lived. The expected happens. Thenali falls in love with Janaki (Jyothika), the younger sister of Dr. Kailash, which was vehemently opposed by the latter. The whole film is about how Dr. Kailash goes mad with the antics of Thenali and even begins to suspect that his wife has an affair with Thenali, as she has a soft corner for the latter. He even tries to kill Thenali by tying him to a tree with a time bomb, which Thenali (not knowing it is a bomb) removes and puts it in the doctor’s house, causing it to explode and Dr. Kailash, seeing this, suffers a paralytic attack.