Vazhthugal revolves around Kathiravan, a successful entrepreneur who manages a software company. Kathiravan is an affectionate son and socially responsible too. His company is involved in various social activities.
When his close friend’s parents are forced by their daughter-in-law to leave home, Kathrivan decides to marry a girl who will keep his parents happy. While watching a television programme he is impressed by Kayal, a college student from Coimbatore being interviewed on a show.

Thiru, a local gangster, falls in love with Charu, an NGO worker, and decides to marry her. He changes his profession and starts a new life, but the police arrest him for his earlier crimes.

Deepika (Bhavana) is an arrogant rich girl. A medical college student, she dictates terms at the college. Sister of local don Kasi (Prakash Raj), she is feared by students, professors and even the Dean of the College. Enter Aarya (Madhavan), a final year student who comes to Chennai Medical College from Coimbatore. A soft-spoken Aarya runs into Deepika. They develop cold shoulders. In a fit of rage, she kidnaps Aarya’s sister. But Aarya faces her challenges daringly. However, she soon falls in love with him. But he is not ready to marry the sister of a ruffian. The remaining story tells us how the brother and sister put pressure on Aarya to become a rowdy so that Aarya’s status is equal enough as Kasi’s status so that Aarya can marry Kasi’s sister Deepika. Meanwhile, “Snake” Babu (Vadivelu) is elected the area councillor, and has a few encounters with Dr. Aarya, and one with Deepika. He is the main source of comic relief for the film.

Bharat has paranoid schizophrenia however it is revealed only in the end. In the first half he is a good Samaritan, a real estate guy who helps people from land grabbing mafia. In the second half however he is shown killing Dr Srinivasa Iyengar (Nasser), a police inspector Mahesh Deshpande and a minister.

The story is told through the protagonist Murugesan (Pasupathy), who recalls his childhood in Virudhunagar town. His father is a butcher who works hard to bring up his four children (two boys and two girls) and have a happy family. Murugesan dotes on his younger brother Kathir, and his weakness, like any other adolescent, is a love for movies (especially MGR films) that are screened in a local theatre. One day, life changes for Murugesan when his father catches him red-handed from the theatre after he bunks school. Murugesan is severely punished and runs away from home, taking money and jewels.
Along the way, Murugesan gets sidetracked from his intended destination of Chennai by an MGR movie poster. He is shown watching several MGR shows, buying a change of clothes, and eating a hearty meal with his ill-gotten money. After spending the night at local temple, he wakes up to find his money and other possessions missing. Murugesan is then taken under the wings of a theatre projectionist in a nearby town. Slowly, the theatre becomes his home.

Two brothers envy their step-brother Shiva as he is their father’s favourite. Since their plan to deal in drugs and arms is opposed by Shiva, the two brothers hatch a devious plan to bump him off.

The movie begins with an orphan Ganesh (Srikanth) coming in search of a job at a petrol bunk in ECR. He manages to win the goodwill of the petrol bunk owner and gets a job there. Enters Priya (Bhavana), an arrogant college student. He throws a challenge to his friends to make Priya fall for him. Meanwhile, Priya’s brother Vetri (Suresh), a leading criminal lawyer in the city, comes to know of Ganesh’s moves and tries to thwart his plans.

Vasanthi (Bhavana) is the daughter of a man (Lal) who does a lot of help for the refugees. She instantly falls for Jeevan (Jiiva), a Tamil refugee staying in the camp in Rameswaram. Jeevan, nurturing a dream to go back to his homeland, keeps on discouraging the girl, who is stubborn in her love. Jeevan’s heart, influenced by the pure love of the girl, starts melting slowly. Enters Vasanthi’s cousin (Bose Venkat), who is full of dreams on marrying her. He joins as an inspector in the local police station. The whole family is eagerly awaiting their marriage. Problems arise when the family comes to know about the love. Vasanthi’s cousin and his uncle try to eliminate Jeevan. They keep on troubling him, without much success. Meanwhile, the refugees get a chance to go back, and Jeevan has to go with them. He promises Vasanthi that he would come back to marry her. The family is determined to stop him. Vasanthi decides to end her life if Jeevan does not turn up.

Two brothers envy their step-brother Shiva as he is their father’s favourite. Since their plan to deal in drugs and arms is opposed by Shiva, the two brothers hatch a devious plan to bump him off.

The story is set in a suburb of Madurai. Suryan (Bharath) and Chandran (Bharath) are twins. Suryan, the elder of the two is soft spoken guy who works at a local lending library and he falls in love with Manimekala (Bhavana), daughter of Namasivayam (Mahadevan) the local politician-don and MLA. Chandran, the younger one, works as a mortuary assistant in the local government hospital and he’s one among Namasivayam’s bad guys who are in charge of his election campaign. Chandran is romantically linked to a local girl,Tamizhselvi (Sandhya). Namasivayam comes to know about his daughter’s love affair with Suryan and he orders to some killers to kill Suryan. But accidentally they attack Chandran who succeeds in escaping from them.

Venki (Prithviraj) is an entrance coaching professor by day and robs automated teller machines (ATMs) using fake debit cards by night. He has been operating out of Kochi for the past three months and the Imperial Bank of India (IBI) is the target of all these robberies. ACP Harris (Jayasurya) is in charge of the investigation. But the managing director of the bank, Nandakumar Menon (Biju Menon), is not happy with the way the investigations are proceeding as the cops have been harassing the bank’s customers. The bank authorities have ruled out a problem in their systems as the same system is used by other banks. The other banks are not yet a target. All the transactions done by the robber have been using a debit card. Nandakumar Menon decides to conduct an investigation in parallel with the cops. He summons a private Detective Alexander Felix (Narain). Felix is an unkempt young man who opted out of IPS. On the first day, he oversleeps on the train and does not disembark at Kochi. But …

Billu (Jayam Ravi) is the son of Mudaliar (Vijayakumar). Mudaliar is much loved and respected by people of his locality, and Billu is almost like a foster son to every person in the locality.