Three amateur thieves plot to kidnap the young son of wealthy Chettiar (Santhana Bharathi) from school. They do a trial run. However, on the eve of the kidnap, the guy whose job is to operate a crane in this plan is hospitalized. The services of Avinasi a.k.a. Mumbai Xpress (Kamal Haasan), brother of Kovai Sarala, a deaf stuntman performing daredevil bike acts, is roped in. Twists and turns take place where the other two gang members are hurt, and invariably, our Mumbai Xpress is left to perform the task all by himself. He kidnaps a wrong boy Daddu (Hardhik), the illegitimate son of Ahalya (Manisha Koirala) and police officer Rao (Nassar), but manages to get a huge ransom from Chettiar by default. A brawl takes place between the original kidnap planners – Chidambaram (Pasupathy), Johnson (Vaiyapuri), and Avinasi – in handling Ahalya’s child, but Avinasi delivers the child unhurt to his mother.

Ram’s friends hire Maggie, a call girl, to help him get over his wife, who mistakenly believes him to be a philanderer. However, they get in trouble when Maggie ends up dead.

Krishnaswamy (Kamal Haasan) is a widower living happily along with his mother-in-law Saraswathi (S. N. Lakshmi), daughter Kaveri (Mahanadi Shobana) and son Bharani (Mahanadhi Dinesh) in a village near Trichy. Dhanush (Cochin Haneefa), a con from the city, has an eye on Krishna’s prosperity and asks him to join his chit fund business. At first, Krishna is reluctant; however, when a rich friend from a foreign country visits his house, he too wants to be rich like them. Hence he agrees to Dhanush’s proposal and arrives at the city. However, he is unaware of Dhanush’s tricks and when Dhanush swindles away the chit fund money, the blame is put on Krishna, and he lands up in jail. He finds that even his future father-in-law Panjapakesan (Poornam Viswanathan) is also in jail for the same reason, whose daughter is Yamuna (Sukanya), working as a nurse. He advises Krishna not to be angry if the jailor is cruel, as he might be released sooner if he is submissive in the jail. During Krishna’s tenure in jail, Yamuna takes care of his family. Due to unavoidable situations, his mother-in-law dies and his children go missing. Krishna learns this after coming out from jail suffering unnecessary hardships.

Venugopal, a wealthy industrialist, marries a woman named Sushila and they have quadruplets. His brother Nandagopal tries to have her and the newborns killed by hired goons. However, the leader of the goons has no desire to kill the babies, so he adopts one (Michael), leaves one in an orphanage (Raju), one in a temple (Kameshwaran) who is picked by Palakkad Mani Iyer, a Brahmin, and one (Madhan) in a car that belongs to Venugopal.
30 years later, Madhan is now a London-educated businessman. Venugopal has raised Madhan as his adopted son, not knowing that he is his biological son. Venugopal is killed by Nandagopal and his nephew, Ramu for his inheritance, but unknown to them, the will has already named Madhan as the beneficiary.

Rangan, an unemployed man, follows stringent principles which make it difficult for him to cope with the corrupt world around him. Resultantly, he struggles to land a job and lives in poverty.

An anti-government union leader’s only son Sakthivel is arrested by the police to find his whereabouts. They trick Sakthivel into believing them as his well-wishers and release him. When Sakthivel meets his father, the police kill the latter. Feeling betrayed, Sakthivel stabs the police inspector and runs away to Bombay, where he is raised by Hussain, a kind-hearted smuggler living in the Dharavi slums.
One day, when Hussain is ill, Sakthivel, now a young man, decides to carry out the smuggling activity on behalf of Hussain. His demand for a bigger commission from the smugglers makes them furious and they involve a police inspector Kelkar to arrest Hussain and kill him in jail. When they close the case as suicide, Sakthivel is angered knowing the truth and murders Kelkar. He later takes care of Kelkar’s family which consists of his wife and a mentally challenged son Ajit. Kelkar’s wife knew that her husband’s immorality resulted in his death.

Bio-scientist Govindarajan Ramaswamy speaks at the Jawaharlal Nehru Stadium about chaos theory and the butterfly effect. He begins by reciting events from the 12th century in Chidambaram, when King Kulothunga Chola II, a Saivite, persecutes Vaishnavites and intends to destroy an idol of Govindaraja. Rangarajan Nambi, a Vaishnavite, protects it and offends the king, who orders Rangarajan to be executed by being pierced, stoned, submerged into the sea with the idol, before being devoured by the shark, thus the king succeeding.
On 20 December 2004, a nano bio-technology lab in the United States designs a vector-virus intended as a bio-weapon. When they were watching the insound of his lab monkey breaking out of his cage and retrieving a sample of the test virus. The monkey, who thinks the vial as the usual chocolate Govind would feed him, swallows the sample of the virus. Govind and his co-workers watch helplessly as monkey dies. Govind, saddened by the event, quarantines the lab room by filling it with concentrated salt solution, the only antidote to the virus. After understanding the original virus’s lethal potential the hard way, Govind refuses to hand over the main single vial containing the virus, due to fear of misuse. However, his boss, Dr. Sethu, has a malicious plan in mind, and tries to sell it to a terrorist group. Govind tries to sneak the vial out of the lab in order to save the vial from Sethu’s evil plan, but is pursued by the security guard and the police. Govind flees to his friend and coworker Suresh’s house for refuge, who secretly betrays him.

Anand, a wealthy man, spends his time in drinking, gambling and entertaining his friends. When he meets Geetha, a young woman, he is smitten by her and decides to mend his ways.

Chinnadurai (Major Sundararajan) owns a huge estate that grows and processes tobacco and tea leaves. Due to advancing age, he is concerned about leaving control to his son, Kalyana (Kamal Hassan) and the cunning deceit of his manager, Ramiah (Thengai Srinivasan). Kalyana is immature and naive, and easily manipulated by the cook, Samipillai (V.K. Ramaswamy). He is also deeply in love with Shenbagam (Sridevi). Ramiah, Samipillai, Perumal (Senthamarai)(Shenbagam’s father), and Ligappa (a hired thug) plot to murder Chinnadurai and swindle the property from Kalyana. Ligappa mortally wounds Chinnadurai, and on his death bed he confesses to his son that he was born a twin, abandoned his first wife Rajulakshmi (Puspalatha)and his brother Raman (Kamal Hassan). After his father’s death, he conveys this information to the cook, who tells him he will go to Madras and bring his relatives home. Instead, Samipillai goes to a side show, and hires a married couple Rangamani (Manorama) and Kittu, to pretend to be the lost mother and son. One day the entire gang is in a room, laughing at how they had duped Kalyana and will steal everything. He overhears, and runs to tell the police. They chase after him and throw him off a cliff, observed by Shenbagam, who goes mad. Kalyana’s ghost travels to Madras and confides everything to his brother, Raman. He wants his brother to go home, exact revenge, and take care of Shenbagam…..

Vasool Raja- is in a rowdy gang, where they get money from people. When his parents are coming for a visit,he & his gang pretend they are running a hospital. Later Vasool’s parents find out that they were cheated by their own son as pretending to be a doctor. Now Vasool must attend a medical school to earn his parent’s trust back. There he encounters his love at first sight (childhood friend) and he encounters his arch-enemy.

The film starts in a courtroom where a woman Janaki (Meena) is fighting for divorce from her husband Pandian (Kamal Haasan). She offers various reasons for wanting a divorce. She has married Pandian against the wishes of her rich father Vishwanathan Iyer (Gemini Ganesan). But she isn’t able to come to terms with living in Pandian’s small house without amenities. Pandian is an assistant dance director with a modest income and is not able to spend much time with the family. All this accumulates and Janaki decides to apply for divorce, which is granted. The court orders that Pandian can meet his daughter Barathi, once a week and this is his only solace. His daughter, however, loves him a lot and doesn’t like the arrangement. Basha (Nassar), Pandian’s Muslim friend who works in a hotel as a chef, advises him to steal his daughter from Janaki. Pandian goes about trying to do as his friend suggests. In doing so, he is discovered; and now he cannot meet her at all. Then Pandian finds out that Vishwanathan Iyer has advertised for a woman to look after his granddaughter. Joseph (Nagesh) is a makeup man in films. In conversation with him, Pandian gets the idea of playing an old woman, so that he can be with his child and ex-wife without knowing them. Joseph agrees to this plan and the transformation is done from Pandian to “Avvai Shanmugi”– (also Kamal Haasan) a dignified, elderly Iyer woman, who is hired to take care of the little girl.

Raja and Devi fall in love with each other and get engaged. However, when Raja learns that he is suffering from cancer, he hides it from Devi and calls off the engagement.

Arun (Ramesh Arvind) is married to Leelavathi (Kalpana) in a forced marriage. He is embarrassed by his wife’s plain looks and her weight. When he meets Priya (Heera Rajagopal) – who works in a building construction company, he hides from her the fact that he is married and has an affair with her.
When he takes Priya with him on a vacation to Bangalore, he bumps into his old friend Dr. Sakthivel Gounder (Kamal Haasan) – an orthopedic surgeon from Coimbatore who is also in Bangalore with his wife Palani (Kovai Sarala) and his son Anand – travelling with him in the same flight and even staying in the same hotel. Sakthivel is called to Arun’s room in the night – as Arun has slipped his disc and the hotel doctor is unavailable – and bumps into Priya, thus finding out about the affair.

Nandu and Vijay are brothers, who were abused by their stepmother during their younger days. Nandhu, who is mentally ill, decides to kill Vijay’s fiancee as he visualizes her as his stepmother.

A young agriculturist Velu (Kamal Hassan) goes to extremes to attain revenge against his devious landlord and her family. He is an upright young man, but when his family gets cheated out of money, he decides it’s time to take a stand. Donning various disguises, he-with help from his sister Valli (Thulasi)-sets out seeking justice against the landlord and her confrontational daughter Geetha (Ambika) and son Pazhani (Raveendran).

Finding it hard to put his dark past behind him, Samar grows to despise girls and indulges in women trafficking. Arrested and put in an asylum by the police, he falls for a demented lady prisoner.

A veteran freedom fighter named Senapathy learns a rare form of martial art that enables him to kill anyone with his bare hands. He uses that to end crime and punishes the culprits on his own.

A young woman regresses to childhood after suffering a head injury in a car crash. Lost, she ends up trapped at a brothel before being rescued by a lonely school teacher who falls in love with her.

Rajalakshmi raises Ramu, an orphan, as her own son who in turn always protects his foster family. However, he must stop his malicious foster brothers from marrying off their real sister to a gangster.

A spoiled young heiress marries a poor man in order to inherit her grandfather’s property.

Nirupama, an ambitious woman studying in the USA, marries a dance master, Viswanathan. On being suspicious of his behaviour, she hires a detective, who reveals his true identity and past.

When stuntman Sambandham (Kamal Haasan) and Dr. Janaki (Simran) come across each other at his brother Anand’s (Abbas) and her best friend Malathi’s (Sneha) hastily planned wedding ceremony, they instantly develop a dislike for each other. They both have a very low opinion of the opposite sex, and staunchly believe marriage is not the way to go for the two newly-weds, whom they try to discourage from proceeding further.
Janaki convinces Malathi to test out her theory that men are after only one thing, by forcing Malathi to delay their consummation for three months. She is sure Anand will not be able to do so and this will prove to Malathi that Anand is just another low-class male, like all others.