An IIT gold medalist gets pulled into the Indian Administrative Services, where he confronts the newly elected political establishment.
Singam (Krishna Sekhar) gets cheated out of an original idea of his by a prominent person in the society. He decides to stop pleading and start threatening. He begins with a plan to corner the big shot. He meets Krishnaveni (Vijayalakshmi Agathiyan), who has left home and needs fast money. With a common purpose, they soon become partners and work out a plan. They blackmail the big shot with videotapes that they threaten to release all over the media if he refused to pay up. Buoyed by the success of their maiden outing, they decide to become con artists. They are successful in various ventures and finally end up blackmailing a minister. The minister, after initially caving in to their threats, decides to settle scores. What happens next forms the rest of the story.
Jagannathan (Sarath Kumar), fondly known as Jaggubhai, is a tough, upright, straightforward Indian police officer with sharp methods. His way of dealing with the criminals strikes terror in the underground world. Jaggubhai is sent to Australia on an important mission to deal with antisocial elements there. In Australia, he meets Ilavarasi (Srisha), and they fall in love with each other. Jaggubhai fails in his mission for which he came to Australia, and the brief romance with Ilavarasi ends abruptly. Jaggubhai returns to India as a dejected officer, failing in his official duty and personal life. Fate had something in store for him. 20 years later, or as he says it 21 years later, he gets a call from Australia stating Ilavarasi is dead and has left him a will. He reaches Australia and is shocked to know the brief encounter with Ilavarasi had resulted in a daughter Monisha (Shriya Saran), now a teenager.
A group of college girls, driving a light blue matador, arrive at Chola Picnic Village. They book a hotel room with a picnic spot. At night they go out to the beach, light a bonfire, and enjoy singing and dancing. After the song ends, the girls return to the hotel. One of the girls, Vasanthi, separates from the group. She comes across a pi-shaped bell stand and rings it three times. A man, P.R.K, appears, riding on a carriage. He looks into her eyes, and rides Vasanthi down, grabbing her hair and kidnapping her.
An NRI returns to his village with his family with a mission to better the lives of the village natives. But in a sudden turn of events, the NRI is left helpless, as a fellow villager steals the money and flees. The villager is now the head of a huge business empire, which is a result of his corrupt activities. The NRI returns, this time for vengeance.
Ennaku 20 Unakku 18
Sridhar (Tarun) is a final year degree student and gets selected in the campus selections for studies abroad. He goes to Mumbai for an interview and in his return finds Preeti (Trisha) and loses his heart to her. Sridhar comes to know that Preeti was about to join in degree and Preeti learns that he was a final year degree student. Sridhar is an ardent cricket fan, so is Preeti, while Sridhar is also a good football player. The principal of the college appoints a coach called Reshma (Shriya), who is also a student, for the football team led by Sridhar. Sridhar tries his best to trace Preeti by visiting several women’s colleges, while Preeti also watches for Sridhar at the men’s college. Accidentally, Preeti helps Sridhar’s mother, when she had a heart attack. In order to find Preeti at any cost, Sridhar goes to the LB Stadium, where a cricket match is in progress and gets injuries in a bomb blast in the stadium. Just before the blast, both Preeti and Sridhar find each other but could not meet due to the blast.
Maaran (Sathyaraj) is a clerk in the district collector’s office. His life centres around his loving wife (Seetha), his son (Raghuvannan), and his daughter (Preethi Varma). Soft-spoken, and a Gandhian to the hilt, Maaran does not stand by any smear on the Mahatma’s name. Being a staunch patriot, he had even named his son Sudhandhiram.
Marudhamalai (Arjun), a police constable, goes to work in the village of Nachiapuram after passing his police exams and getting a merit. Here he meets ‘Encounter’ Ekambaram (Vadivelu), his senior officer. He is asked to do all sorts of work for him, and one day, Marudhamalai loses a convict on the way to the court due to Ekambaram’s soft heart. He then is to clean the floors of the inspector’s house and there he falls in love with Divya (Nila). Then, later in the market, after Ekambaram is humiliated by a beggar, Marudhamalai sees Maasi (Lal), the ‘boss’ of the city, killing a person who stood for a candidate in the elections. Then the election commissioner comes to the place, and he discovers that elections have not been held for 16 years in the city due to Maasi’s opposition.
Kathir (Bobby Simha) has an interest for Anbu (Tanya Ravichandran), but due to family situations, she gets hitched to Karuppan (Vijay Sethupathi). What does Kathir do, to separate Karuppan and Anbu, and does he finally get to marry Anbu?