Salman Khan plays Prem, married with 2 kids, who gets involved in a roaring affair with an aspiring model, Rupali. He prefers Rupali to his wife because Rupali is modern and wears fashionable clothes. On Karwachauth, Pooja (his wife) discovers him at Rupali's house and asks him to choose between his mistress and his wife. He decides to move in with Rupali and starts living with her. His wife, Pooja, meanwhile with the help of Salman's friend Lakhan (Anil Kapoor) has a make-over. She becomes the modern woman who does many modeling assignments. Also, Pooja sends her mother-in-law and children to live with her husband and Rupali. They all trouble Rupali and manage to convince Prem that Rupali keeps them hungry and wants to poison and kill them.
In the end, Prem realizes that Rupali only came to him since he gave her materialistic things while his wife stuck with him through thick and thin. Rupali also realizes her mistake and gets back together with her ex-boyfriend, played by Saif Ali Khan. In a twist, Lakhan makes Rupali his sister and is hugging her when his wife Lovely (played by Tabu) walks upon the scene and misunderstands them both. She leaves the house crying and drives away in a car, which their son has tampered with and has managed to disable the brakes. Lakhan then chases after her and makes up with her.