Panchathantiram is a Tamil language film starring Kamal Haasan and Simran Bagga in lead roles of the protagonist. Ram (Kamal Haasan) is a pilot based in Canada and an irredeemable skirt-chaser. In course of a midair hijack situation, he meets Mythili (Simran).
They fall in love and get married. Ram's four closest buddies Nair (Jayaram), Iyer (Yugi Sethu), Hegde (Ramesh Arvind) and Reddy (Shriman) are present at the wedding --- minus their wives. One day, when Ram helps a damsel in distress, Mythili misinterprets and presumes that he is two-timing her, and flies off to India to her parents' home. And Ram goes chasing after. Further misunderstanding occurs when he goes to meet Mythilli, drunk and in the middle of the night.
To take his mind off Mythili for a while, his four friends drive him down to Bangalore and fix him up in a room, complete with call girl Maggi (Ramya Krishnan). Ram won't have any of it. He gets into a fight with Maggi, then dashes over to his friends' room. To salvage the situation, Iyer hurries off to Ram's room and finds Maggi dead. Panicking, decides to get rid of the body inspite of Ram’s pleas to call the police. They manage to roll the dead body in a blanket and carry it over to their car. A mysterious ‘Sardar’(Ramesh Krishnan) watches over this. The friends dispose of the body in a river and drive over to Chennai to lead their normal lives.
Ram discovers a cache of diamonds inside the dead girl's cell phone and spoils the plans of the Sardar to steal them. Meanwhile, Mythili is goaded by her parents to give Ram one more chance and she arrives at Ram’s house. In the tussle with the Sardar, Ram removes the Sardars hat and mythili mistakes the Sardars long hair for a girl and leaves Ram once again. The Sardar manages to escape.
The friends get very nervous when they learn of a news article regarding the discovery of a dead body in the same area that they disposed off their dead body. A traditional festival has the wives of the four friends plan a party. While planning, Mythili overhears a conversation among them regarding their husband’s friends Ram’s fight with a Sardar and how his wife thought that it was a girl he was having a affair with. Mythili reveals her identity to the wives and gets invited to the party to be rejoined with Ram.
As everyone is present in the party, a twist comes when the supposedly 'dead Maggi' lands up, demanding her diamonds back. She then reveals the truth. The diamonds belongs to her diamond smuggling boyfriend (Manivannan) and she had stolen it from him. She saw an opportunity to make everyone believe she is dead when Ram’s friend mistakes ketchup to be blood and thinks that she was dead. The dead body belonged is of her boyfriends other girlfriend that she killed and managed to get into the blanket when the friends weren’t looking.
Ram with help from his friends, and the Sardar, who happens to be an undercover police officer trying to find the diamonds, saves everyone from Maggi and her boyfriend. Mythilli, promises to change her over suspicious ways and both get back together.