Plot

Raj (Bobby Deol) and Priya (Kareena Kapoor) meet by chance (Priya was thinking that Raj was stalking her when in reality Priya had walked away with her umbrella at the church) and fall in love after a whirlwind romance. Raj gets a job at the polo club, where Priya's dad (Dalip Tahil) is the chairman.

They marry and reside in Switzerland, where they meet another Indian couple: Vikram (Akshay Kumar) and Sonia (Bipasha Basu). The couples quickly become friends and decide to go on a Christmas vacation together to Mauritius. Raj was against going to Mauritius as he is not as wealthy as Vikram. But Vikram fakes an accident and gets a payout of $50K on his accident insurance policy and offers that money to Raj to convince him to come. Priya insists that Raj should go, Raj agrees to wants to pay for his own and Priya's expenses.

During their vacation, Raj sees Vikram with another woman, kissing and looking intimate. At the same time, Sonia begins to try to seduce Raj, who rejects her. Vikram notices Raj looking at Sonia and casually talks to him about wife swapping and Vicky casually suggests Raj to enjoy with Sonia and asks whether he (Vicky )could enjoy with Priya overnight , this upsets Raj and an argument breaks out between the two men. Raj takes Priya away from Mauritius. However, a couple of days later Vikram and Sonia also return, Raj & Vikram they resolve their issues and become friends again (Raj saves Vikram's life when a car falls on him when he was working under it for repairs). On Vikram's birthday, the two men celebrate by getting drunk together, sharing bottles of alcohol. Once again, Vikram asks whether he could become Raj for one night, which Raj rebuffs, but still, both men end up in opposite houses.

The next day Raj wakes up to find a semi-naked woman in bed and realizes he is in Vicky's house. After talking to Priya about the events from last night, he imagines Vicky was able to seduce and convince Priya to go ahead with his wife swapping and making passionate love throughout the night (Although Priya never said anything to that effect, but her half sentences gave that impression).

After some time, Sonia is found dead, and Raj is accused of her murder by Vikram saying that Raj spent the whole night with Sonia and additionally his fingerprints are found on the murder weapon - an alcohol bottle. Priya is shocked as she never did anything with Vikram. In jail, Vikram visits Raj and offers him 14 Lakh dollars if he admits to killing Sonia and takes the punishment of life imprisonment (14 yrs). In court Vikram says that Raj took him to the airport bar after leaving the wives at home. But neither had money, so Raj went back to bring his wallet, but instead went into Vikram's house to sexually assault Sonia. Sonia resisted and Raj killed her. However, one of Raj's neighbors is also in court and he remembers seeing that 2 men entered Vikram's house and not one. Raj alleges in court that he went into Vikram's house to warn Sonia about his errant behavior, but then passed out.

Determined to prove his innocence, Raj manages to escape from the court and is chased by the Swiss police. He meets Priya, who eventually believes his innocence and aids him in finding out what really happened. Raj tells Priya that he never went to the airport bar with Vikram and wants to prove this. They meet their neighbor who tells Raj that Vikram left alone that night. But later that night 2 men returned to Vikram's house (when Raj was already inside). He decides to search Vikram's house, only to be interrupted by Vikram, who calls the police and then reveals that everything was planned in advance. Raj escapes in Vikram's car with Priya.

Raj finds a boarding pass that belongs to Sonia Bajaj from her book in Vikram's car, which states that Sonia arrived in Zurich on 29 December - however, Sonia was supposedly murdered on that night. Raj suspects her to be the woman he saw with Vikram, traveling to Geneva together. In Geneva, Priya finds the address of the woman who bought the ticket to Zurich for the 29th Dec. At her house, Raj finds an insurance officer who is trying to find evidence that Vikram was involved in the death of his wife, in order to receive her life insurance payment of $100 million.

Working with the insurance agent, Raj traces Vikram to a cruise ship. There, he sees Vikram dancing with a woman who is revealed to be 'Sonia', alive and well. Raj confronts Vikram, who finally explains the whole devious plan - the woman whom he kissed in Mauritius was his actual wife Sonia Bajaj (Mink Brar), while the woman with him that Priya and Raj were introduced to in Switzerland is his girlfriend Neeta. Vikram, a struggling musician, married the wealthy and glamorous Sonia and convinced her to take out an insurance plan of $100 million on herself.

That night, Vikram went to the airport to pick up the real Sonia. He went to the bar to get a witness that he was there, and slipped out to take Sonia home. The neighbor saw Vikram and Soni entering Vikram's house. Vikram used Raj's champagne bottle to kill Sonia and disfigure her face. Then he put Neeta on the flight to Geneva and went back to the airport bar to stay there till the morning.

Vikram boasts about having pinned the murder on Raj. However, Raj takes Vikram to a computer and shows him his empty bank account. Raj says that he had guessed the password, "Everything is planned", something that Vikram used to say a lot, and used it to transfer the money back to the insurance company. Raj also reveals that everything Vikram said had been recorded. A fight erupts between the two and Neeta dies in the conflict. Angered at losing Neeta, Vikram gets aggressive, killing the insurance officer and seemingly kills Raj. He chases Priya to kill her too, but Raj is able to save her. Vikram dies when he is impaled by an anchor from the cruise ship. Raj and Priya return to India in the end.