Janaki and Pappamma are employees at a fashion export company. Janaki is a shy Brahmin woman who works as a typist to support her family after her husband lost his factory job. Pappamma, who lives with her drunkard rickshaw-puller husband and earns a living for both of them and her husband's drinking expense, is a housekeeper there. The women in the company face a common threat from their manager, G. K. Pandian. Although married, he is a womaniser, and harasses his female employees regularly. The women tolerate his behaviour because of their family circumstances.

Sathya, a computer graduate, joins the company as a designer. Noting her intelligence and beauty, Pandian attempts to get closer to her. Initially believing his overtures are strictly platonic, Sathya accepts an invitation to dine with him. This is noticed by the other employees who misread the situation and shun her. When Pandian presents her with a silk sari, Sathya understands his actual intentions and rebukes him, gaining the respect and friendship of Janaki and Pappamma, who are fed up with their manager's antics. As their friendship blossoms, Janaki becomes increasingly courageous and speaks up when treated unfairly, a point noted sourly by Pandian's sidekick, Madhavi.

One day Pandian asks Janaki to work late. Asked to prepare him a coffee, she unknowingly mixes rat poison in his coffee instead of sugar and gives it to him. Pandian falls from his chair and becomes unconscious. Sathya finds him and he is admitted to the hospital. Janaki realises what she did, thinks Pandian drank the coffee and tells Pappamma. Both rush to the hospital and tell Sathya. The trio are unaware that Pandian fainted because of a minor injury and has recovered. They overhear that a patient (a terrorist) is dead from consuming "poison" (cyanide). They steal the covered corpse, assuming it is Pandian, and take it to Sathya's room, only to find that they have taken the terrorist's corpse. Panicking, they decide to return the body to the hospital. After several mishaps, the police take the body away.

Pandian returns to work. On learning what happened from Madhavi, he blackmails the trio into spending three nights with him in his guesthouse. He tells them if they refuse, he will have them arrested. The trio appear to agree, but once they reach the house, they overpower him, tie him up and imprison him in a room. Sathya takes charge as acting manager in the office and, with the help of Janaki, Pappamma and the other employees, brings about many changes there. Sathya soon receives information from the head office about the boss's visit. The trio is in a quandary since Pandian is still in their custody. The trio decide to come clean about what happened and rush to the airport to pick up the boss who they have never seen. However, Madhavi overhears them and rescues Pandian, and they head to the airport. The trio arrives at the airport but misses the boss who leaves with Pandian. They rush to the office.

On reaching the office, the boss finds it has changed radically. A flustered Pandian says that he is not responsible for this, and blames Sathya, Janaki and Pappamma. However, the boss appreciates the trio for their innovative ideas, and tells Pandian he is aware of his misogynistic behaviour and harassment towards his employees, relayed to him by a spy he had planted in the office. He leaves the trio in charge of the office and transfers Pandian and Madhavi to Andaman. He offers Janaki's husband a job in his friend's factory and Pappamma's husband a job as a watchman in their school, delighting them. When he inquires about Sathya's marriage, Janaki says that she has an artistic rendition of her dream husband drawn in her computer. Sathya shows him her rendition, and they are all surprised to see that her dream husband looks exactly like their boss. The boss asks Sathya to marry him, and she accepts his proposal.