The film opens with the ageing gangster, Singaperumal, forcing himself on a young girl, Subbu. He is unable to perform, and vents his anger by slapping the helpless Subbu. Singaperumal is the grand don of crime in Madras. His lieutenant, Pasupathi, brings a proposal. A large stash of cocaine, worth about ₹ 2 crore, has entered the city. The guy bringing the stash wants to sell it for ₹ 50 lakh. Pasupathi sees the immediate easy profit, as well as the long term benefit (to control the cocaine market with such a large supply) and the recognition that they are able to pull off such a deal. The drawback is that the stash really belongs to their arch-rival Gajendran. Singaperumal knows that Gajendran is a vicious and unpredictable adversary, and the venture is risky and likely to become messy. He decides to pass. Pasupathi dourly suggests Singaperumal is getting old and rusty. He asks Singaperumal to loan him the ₹ 50 lakh so he can do the job himself. Pasupathi is prepared to face the risks, and in return for the loan, he offers Singaperumal a cut of the profits. Singaperumal agrees to the loan, but, instead asks Pasupathi to first get the stash and then think of the profit distribution. The money for the loan is brought to Singaperumal.

Arvind, an ordinary Joe who is not noticed by any, be it at home, school or among friends falls in love with Janani, a class topper and an all-rounder who excels in sports and extra-curricular activities. A loner by nature, he is smitten by Janani and in his quest to be closer to her, he even enrolls himself in the same college where she studies. But, sadly, Janani is neither able to recall his name nor remember them being classmates in school. And she rejects him when he expresses his love for her. Kootathil Oruthan captures the journey of Arvind, an ordinary middle-bencher, and his travails after being rejected by the love of his life.

On the way to Chennai, Bala’s (Srikanth) bag and certificates get stolen in the train. But he has a look about him that endears him to a petty shop owner Sundaram (Haneefa), who provides him accommodation along with a few bachelors (Vayyapuri, Shyam Ganesh and Sukran) in the top portion of his house. Malar (Trisha) stays opposite this house and the bachelors are crazy about her. They are scared if the handsome and generous Bala will try to woo her and so they hatch a plot and frame him, so that Malar’s two brothers beat him up black and blue. Three strangers, who claim to be his true friends from Hyderabad, save an unconscious Bala. Now the true identity of Bala is told in a flashback by these friends, that he is a rich son of an industrialist (Rajeev and Fathima Babu). Malar saves Bala from an accident and soon they are in love. But her brothers take her back to Chennai, as her sister had already eloped with someone. The brothers do not want her to commit the same mistake and make her promise that she will only marry someone of their choice. Then there is another secret that nobody knows – Malar is suffering from some brain disease and will die soon. Bala comes to stay opposite her house to see and make her happy till the end.

The marriage of Meera, a college student, and her boyfriend Saravanan has been approved by the family. But the condition is as after a job after graduation. But when Meera becomes pregnant, the whole story gets upside down

Manoranjan (Kamal Haasan) is a leading film star who is immensely popular among his fans; however, he is beset with several personal problems. 25 years back, he had been forced to marry Varalakshmi (Urvashi), the daughter of noted film director Poornachandra Rao (K. Viswanath), despite being in a relationship with a woman named Yamini. He is an alcoholic and his teenage son Manohar (Ashwin) despises him. He has a daughter Manonmani (Parvathy) who was born out of wedlock to Yamini and was raised by Yamini’s husband Jacob Zachariah (Jayaram) after Yamini’s death. She also despises Manoranjan. He has been diagnosed with advanced stage brain cancer and has only a few more months to live, which is unknown to anyone including his own family. He is treated by his family doctor Dr. Arpana (Andrea Jeremiah), with whom he has an extramarital affair.

The film deals with a ghost seeking vengeance for being wronged and haunts everyone who is staying in the house.

The security guard of a mall, who belongs to the Gurkha community, becomes the saviour of several people who have been kept under siege by some terrorists.

A doting wife goes through a hard time trying to save her husband who is possessed by two spirits.

A Business Fight between Young Entrepreneurs who start an Internet Radio Station, and A Magazine Publishing Corporate. The Internet Radio station hosts a Talk show on Marriage and Matrimony which kindles crazy thoughts among the public.

Raasaiyya (Prabhu Deva) lives with his grandfather, Shyamsunder (Vijayakumar), a kind-hearted and honest man in a small town in rural Southern India. Shyamsunder is very easy-going and permits Raasaiyya in indulge in all kinds of precocious activities. When young and beautiful Anita (Roja) comes to stay for a few days with Shyamsunder, both Raasaiyya and she fall in love with each other, and would like to get married. But Raasaiyya is unable to assert himself, and Anita’s marriage is arranged with a U.S. settled groom. Shyamsunder would like to present a decent dowry for Anita, which includes a priceless diamond necklace. Unable to bear his separation from his sweetheart, Raasaiyya decides to tell Shyamsunder about this, but before he could do so, he finds out that his biological mother, Madhavi (Raadhika), is still alive, but will not have anything to do with him. Watch what happens when Raasaiyya finally meets her and finds out the secret why she abandoned him in his childhood.

Karthik (Gautham Karthik) is a middle-class boy gifted with extrasensory perception who works at an IT company. He has a girlfriend Priya (Priya Anand). During school days, he scores good in the exams using his power, so his father (Vasanth) asks him to suppress this power. Then Karthik meets Pandian aka Panda (Vivek) at his office and befriends him. Panda, a gambler, gets to know about Karthik’s power and asks him to play cricket gambling by using his power. Rangarajan aka Rande (Daniel Balaji) is in charge of cricket gambling under an unknown man known as Kumar. Karthik wins a crore in gambling and uses 10 lakhs for his elder sister Gayathri’s (Gayathri Raguram) marriage. Panda, Karthik and Sathish (Sathish) go on a vacation to Goa to spend the gambling money. There, Rande threatens Karthik to play roulette in the Casino Royale ship. Initially Karthik hesitates, but Rande threatens him by kidnapping Priya. Karthik accepts to play. By this incident, Priya comes to know about Karthik’s power. To train Karthik, Shreya (Taapsee Pannu) comes to help. Karthik plays the game and tricks Rande to take his place in gambling. The casino officials arrest Rande. Karthik, with his money won in the gambling with Panda, Sathish and Priya, escapes and goes back home. Shreya helps Rande escape from guards by the saying of Kumar. Rande traces Karthik and takes him to his place. There, Karthik uses his power to fight Rande’s sidekicks and threatens Rande. At that time, a Rolls-Royce Phantom comes and is revealed that the unknown man Kumar is Kokki Kumar (Dhanush), and he asks Karthik to play for him in politics.

Priya Amal Raj (Kajol) lost her mother at a very young age. She is friendly, outspoken, sensitive, yet precocious. Priya is brought up by her dad, Amal Raj (Girish Karnad) who is a clothing industrialist. Since her childhood, Priya is interested in singing, music and church.
Thomas Thanga Durai (Arvind Swamy), a polite, well mannered NRI business man, returns to India from America to look after his father’s James Thanga Durai’s (S. P. Balasubrahmanyam) business. Thanga Durai is a former associate in Amal Raj’s business, and now establishes his own business empire in the same vicinity, opposite to Amal Raj’s factory. He boasts of his sons achievements. However, Amal Raj dislikes Thanga Durai’s ill-mannered, clumsy and bizarre antics though Thomas and Priya have known each other in their childhood.
Thomas, happens to meet Priya at her school when he goes to a woman’s hostel to see his aunt, Mother Superior (Arundhati Nag) a nun in that school church. Thomas takes Priya’s help in surprising his aunt with a gift on her birthday. In the process, Thomas falls in love with Priya but is unable to confess his love for her. Priya has been brought up in a convent school and wants to become a nun, much to the horror of Thomas and Priyas father. Meanwhile, Amal Raj tries to pull Priya into wedlock through setting up match making with some suitors like Jaipal (Prakash Raj), David (Ranvir Shah) etc., but he fails to fix an alliance for his daughter. In the midst of this, Thomas’s friend Shiva takes him to hairstylist Deva (Prabhu Deva) who is notorious at changing women’s minds. Deva befriends Priya to change her mind about being a nun.
At one instance, Priya performs singing at a Gala along with Deva’s troupe, which puts the troupe into the limelight of a recording theatre owner. Deva requests Priya to join his aspiring music troop as a singer and help them achieve the group’s aspiration for a film audition and Priya agrees to it. Deva with his musical troupe (Nassar and his group) play tricks to make Priya fall in love with Thomas, but fails to turn Priya’s mind towards Thomas. Instead, Deva himself falls in love with Priya and she reciprocates.
Complications arise when Priya falls in love with Deva instead, and at the same juncture, Thomas confesses his love to Priya and reveals the shocking truth behind Deva’s association with Priya. Torn between the two men, a broken-hearted Priya decides to vow for Nun trainee and fails to fulfill her promise for the group’s music audition. Thomas realises this at the end and sacrifices his love. Thomas and his Aunt convince Priya out of celibacy and marry Deva. Thomas becomes a priest as he naturally leads a life of service to the poor, sacrifice and mental chastity.At the climax, it is shown Deva and Priya get their daughter baptised by Thomas.This is the plot of the story.