Rahul Kapoor (Imran Khan) is on his way to become a copy of his parents when he suddenly loses his job as an architect in Vegas. Afraid that he has let his parents down, Rahul decides to hide the truth from his parents and find another job. By a twist of fate, he meets Riana Braganza (Kareena Kapoor), a quick-witted hairstylist, who is everything he isn't. A series of events lead them to meet on Christmas Eve over a few drinks. Following this night of debauchery, they wake up to discover that they've gotten married. Now, Rahul has more than just his job loss to hide from his parents. They both decide to get it annulled as soon as possible and get an appointment from the court in ten days. Over the next ten days, they have their share of arguments, moments and laughs that results in an unlikely friendship.
Towards the end, Riana and Rahul fly back to India, where amidst reflecting on their childhood past, Rahul attempts to kiss Riana, but Riana deflects. Rahul takes the rejection personally and amidst a family dinner, erupts in anger and divulges the complete truth to his parents and their business partners. As Rahul rushes back to Riana to express his apologize for his behavior, Riana explains that she never intended him to fall in love with her while Rahul argues that her actions led him to believe that she had equal feelings for him. After a night of reflection and thought, both decide to maintain their friendship.
The film ends with both returning back to Las Vegas, finalizing their annulment and moving on with their lives, while remaining good friends, with Rahul still hoping to convert his friendship into love.