Sivaraman (Mohanlal), an unemployed man, comes to Mumbai to find a job. Unfortunately he loses all his certificates but happens to find Govindan Kutty (Mukesh), who also is an unemployed man (from Sivaraman's native place) wandering in Mumbai. They try to get visa from a travel agency but find no way amass the funds required.
Govindan Kutty persuades Sivaraman to participate in a bank robbery planned by Thomas (Cochin Haneefa) and his gang - his stammering brother Tyootty (Jagadish) and Alina (who pretends to be Thomas' lover) - which puts them in more trouble as the robbery ends in vain when they hit Pothuval (Innocent).
Alina secretly informs the police about the robbery and misinforms them that the entire plan was carried out by Thomas. Thomas, before getting arrested, hides the money, and the place is kept secret except to his lawyer, Nambeeshan (Jagathy Sreekumar). Alina pretends love with Nambeeshan to find the place where the money is hidden.
Meanwhile, to find a safe cover Sivaraman and Govindan Kutty plan to impersonate Kunjunni, the grandson of a rich but elderly couple, Thampuran (Nedumudi Venu) and his wife Sethu (Kaviyoor Ponnamma). They haven't seen their grandchild since his childhood.
At the confusion of the moment Sivaraman and Govindankutty end up disguising with the body of Govindan Kutty and the voice of Sivaraman to make up for Kunjunni in front of the blind couple. Pothuval, who knows Govindan Kutty before, makes several attempts to make the old man learn the truth, but all of them fail knowingly or unknowingly much to the luck of the Sivaraman and Govindankutty.
While successfully carrying on, they are interrupted by Radhika Menon who disguises herself as the lover of Kunjunni. She calls on all the relatives of the couple by mocking them. The relatives arrive in the absence of Sivaraman. Finding no-way out Govindan Kutty pretends to have fainted unconscious and he gets admitted to the hospital. Sivaraman comes to his rescue and says that he is Dr. Gopalakrishnan, a friend of Kunjunni from America.
After many successful escapades during their drama, Govindankutty tries to steal the Lord Krishna statue for which he plays a cruel trick by placing a wooden stool in the staircase to injure the old woman which keeps all others out of the house for sometime. Sivaraman engages in a fight with Govindankutty when he tries to leave with the statue he had stolen.
The old man accuses his relatives for the accident and asks all his relatives to leave immediately. Sivaraman and Govindankutty gets desperate as the date for the visa payment was nearing. Radhika gives them the money for the visa and asks them to leave the house. She also reveals that she is Kunjunni's actual lover and tells them that Kunjunni has died in America in an accident and she had come to inform this.
Sivaraman and Govindankutty accept the money and leave the house. Upon leaving, they come to know that the visa agency was a fake one. Having lost all their resources, Govindan Kutty plans to start some new business with the money they have. Sivaraman disagrees to take the money and asks Govindan Kutty not to take the money which they have got for cheating on the innocent old couple.
Govindankutty leaves Sivaraman in anger taking the money with him. Sivaraman returns to the old man and confesses all his mistakes. The old man asks them to continue the drama in front of his wife Sethu, who loves her grandson above all. Sethu comes and calls Kunjunni but she gets no replies but finally gets hold of Govindan Kutty's arms who has returned in remorse.
In the closing scene it is shown that Thomas and Tyootty started a new hambug, Nambeeshan has gone back to his native place and has started farming, his ex-wife (Sukumari) gets married to an younger man, Pothuval started an anti-alcohol society, and the future plans of Alina as still unknown.