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The movie begins with a crying Titu who is worried as his girlfriend Pihu refuses to talk with him. Sonu, his best friend, tells him that she is not meant for him justifying his argument by comparing Titu's caring nature with that of his Pihu's possessive one. Sonu gives an ultimatum to Titu to choose between Pihu and him and Titu chooses his best friend.
Six months after his breakup, Titu's family tells him that a family has shown interest in getting him married to their daughter. He agrees to meet Sweety. The two instantly hit it off. Sweety is extremely caring, sensitive and is the 'ideal wife'. Sonu finds this very fishy, though he admits to Titu that she seems nice but he can't really say whether or not the two should marry just yet.
He later finds out that Sweety was in fact going to marry another man named Rahul but that did not work out as she became dominating, possessive and got drunk and created a scene in Goa. He reveals this to the family and grandmother, who question Sweety regarding the same and she tells her version of story where she had no fault. Titu tells Sonu that she had told him all of this in the first meeting itself and he did not want the family to know about all of this.
On the night of the engagement, Sonu begins warming up to the idea of Titu and Sweety's wedding. However, Sweety reveals that she in fact is a clever female and challenges him that she will throw him out of Titu's life and home very soon. Sonu confides in his friends Ghasite and Lalu about the revelation. They bet amongst themselves to see if Sonu can save Titu from Sweety.
Titu is now engaged to Sweety and this brings a lot of compromises in Sonu's life who was earlier used to living a bachelor life. Sweety changes their care-taker, she walks in on Sonu making out with a girl. She also manipulates the family members and Titu into buying and naming a house after her and Titu. She turns the house into vegetarian and threatens Ghasita of revealing his dirty lies to Dadi.
Sonu foresees Titu's imminent downfall and to protect him he plans a bachelor party for Titu at Amsterdam, where he arranges his ex-girlfriend Pihu to "accidentally" run into them after convincing her that Titu is still in love with her and he wants to help them get back together. They return to India along with Pihu and Sonu is happy to see a bothered Sweety after witnessing the growing closeness between Titu and Pihu. But Sweety reveals the truth to Pihu that it was in fact Sonu who broke Titu and Pihu up in the first place and that Sonu is using her. At this point Titu is visibly angry with Sonu.
He once again confides with Ghasite and Lalu and Ghasite (also Titu's grandfather) volunteers to sort the situation but Sonu interjects saying his best friend should decide for himself. Sonu helps prepare for the wedding, dances in the Baraat but during the garland ceremony he makes a final attempt and gives Titu the ultimatum again: 'It's either her or me'. Sweety attempts to turn the tide but Titu, in a fit of epiphany, firmly announces that if it is between him or her, it will always be his best friend. The scene switches to Sweety standing in the mandap and coming to terms that her malicious tactics cannot always triumph.
After the narrow escape, Sonu, Titu, Ghasite and Lalu are seen sitting and drinking by the pool realizing that good girls do not exist these days.