The film’s central story deals with the organisation of an enormous, chaotic, and expensive wedding that is due to take place in a modern Indian family. Lalit Verma (Naseeruddin Shah) and his wife Pimmi (Lillete Dubey) have arranged a marriage for their daughter Aditi (Vasundhara Das) to Hemant Rai (Parvin Dabas). Hemant is the son of a family friend who lives in Texas, and Aditi has only known him for a few weeks. As so often happens in Indian culture, such a wedding means that, for one of the few times in each generation, the extended family comes together from all corners of the globe, bringing its emotional baggage along.
Lalit and Pimmi are helped with the main planning by Pimmi’s sister Shashi and her husband C.L (Kulbhushan Kharbanda), who have arrived earlier from Oman. A few days before the engagement, Tej Puri (Rajat Kapoor), Lalit’s extremely wealthy brother-in-law, arrives from the U.S.. Tej is married to Lalit’s sister and has helped the Verma family regain their financial footing after the Partition of India left them penniless many years ago. Tej offers to pay for Aditi’s cousin, Ria Verma (Shefali Shah) to attend university in the U.S., after the family consults him for advice. Ria and her mother live with the Verma family, who took them in after the death of Ria’s father. Despite his generous offer, Ria stays away from Tej and is not comfortable in his presence.
Lalit begins experiencing difficulty in paying for the final, smaller aspects of the wedding and is embarrassed when he has to borrow money from friends and colleagues. Meanwhile, P.K. Dubey (Vijay Raaz), the eccentric wedding planner, falls in love with Alice, the Vermas’ maid. Ria grows concerned after she witnesses what appears to be Tej grooming a younger relative, ten-year-old Aliya. Aditi’s younger brother Varun (Ishan Nair) plans an elaborate dance for the pre-wedding party with another cousin, Ayesha (Neha Dubey), but Lalit worries that his son is becoming too effeminate and plans to send him to boarding school. Dubey’s workers see Alice trying on Aditi’s wedding jewellery, and the men accuse her of stealing. The incident causes her to become withdrawn from Dubey and he grows depressed.
A few days before the wedding, Aditi sleeps with an old lover, her married boss Vikram; and confesses this to Hemant. The incident only serves as a reminder to Aditi as to why she stopped seeing Vikram. Though he is initially angry, Hemant is glad for her honesty and is confident that they can put it behind them and be happy together. The workers apologize to Alice and she reconciles with Dubey. The night before the ceremony, Varun refuses to dance due to the comments made by his father, and Ayesha performs with the help of Rahul (Randeep Hooda), Pimmi’s nephew from Australia. Aditi and Hemant grow closer and they share a few intimate moments, which re-affirms their faith in the marriage. After a night of jokes, drama and dances, Ria catches Tej trying to take Aliya for a drive alone. Ria stops them from driving off and takes Aliya away from him, revealing to Lalit and others that Tej had molested her as a child. Lalit’s sister does not believe her, attributing her accusations to her character and unmarried status. Emotionally distraught, Ria leaves.
The next day, Lalit pleads with Ria to return to the wedding, admitting that he can’t possibly imagine what she has gone through but also saying that he can’t disown Tej, since they are family. Ria is not pleased but agrees to return for the sake of Aditi. Hours before the wedding, however, Lalit changes his mind and tells his sister and Tej to leave the wedding and the family home. Tej’s wife insists that Ria’s accusation was a small matter but Lalit stands his ground.
The Monsoon rains begin as Aditi and Hemant are married in an elaborate wedding, while Dubey and Alice simultaneously wed in a simple ceremony, and later celebrate with the Vermas. Ria moves on from her past life, and is finally able to freely enjoy the festivities.