Raj Malhotra, Bobby Deol, Vikram Chopra, Irrfan Khan, and Yogi Mathur, Suniel Shetty, are best friends who run the Virgin Yacht Company in Toronto and share a penchant for flirtation. Their wives Sanjana Arora Malhotra, Sonam Kapoor Ahuja, Shivani Chopra, Rimi Sen, and Maya Mathur, Vidya Balan, are equally close, forming a tight-knit circle of couples whose outwardly polished lives hide a pattern of riskier desires. The trio of husbands manages to keep their affairs relatively well hidden, at least on the surface; Yogi, however, begins to falter as Maya’s secret confidante exposes his indiscretions and threatens the delicate balance of the group.
When Sanjana bumps into Maya, she quickly senses something off about Raj, hinting that he may be lying to her. Shivani, meanwhile, pieces together Raj’s duplicity and quietly suspects that Vikram might follow suit, even as she remains mostly unaware that Vikram is secretly the mastermind behind the trio’s schemes. Maya suggests Sanjana meet Kishen, a private detective with a specialty in extramarital affairs; Shivani appears to know him too, but Kishen’s first brusque encounter with Sanjana has her questioning his instincts until Maya emphasizes that he’s dug up material on Raj. Sanjana leaves unsettled, while Kishen remains determined to prove his points.
At a high-energy New Year’s Eve party, Kishen summons all of Raj’s alleged girlfriends and nearly forces Sanjana to confront the truth, but Vikram steps in to save Raj by convincing Yogi to go along with the ruse. Realizing someone is onto their circle, Vikram reaches out to his intelligence officer friend K.D., who declines to help but advises hiring a private investigator. Fate brings them to Kishen’s office, where they recognize him from the party, completely unaware that he also serves as Sanjana’s informant. Kishen offers to help uncover the “buster” who assisted Sanjana, while secretly playing a double game. He records Yogi’s confession to Sanjana about his affairs and, with the help of a voiceover artist, later doctored an audio clip and a video to show Raj and Vikram. The pair then sabotage Yogi’s hotel date with a woman named Sweety, who is about to marry soon, by tipping Maya off. In the ensuing exposure, Yogi is flustered as Raj and Vikram reveal his duplicity.
Kishen’s next move exposes Raj through a flurry of media stories that paint him as meeting another woman—an elaborate set-up designed by Kishen with her husband’s help. Raj, now on the run, calls Vikram to a waterside rendezvous the next morning, where Vikram reveals a plan to project Raj as an undercover officer on a mission to “destroy” the dreaded criminal King, whose brother was killed—an act attributed to Raj as part of Kishen’s ruse. Sanjana buys the story and forgives him, though she later snubs Kishen after the exposé. Kishen swears to uncover the truth and soon learns from a drunken Yogi about the ploy; he then has Raj and Vikram completely intoxicated and confronts them at a stadium masquerading as King, along with Sanjana and Shivani in attendance. The truth is forced out: Raj and Vikram are compelled to confess their affairs, Shivani collapses, and Sanjana sheds tears.
Sanjana’s immediate response is heartbreak—she contemplates suicide at a cliffside—yet Kishen promises to help her win back the man she knows loves her. He takes Sanjana to her mother Trishna’s home, where her younger sister Kanisha “Kuku” Arora also lives. Though Kuku and Kishen clash at first, she gradually comes to understand his motives. Kishen crafts a plan that casts doubt on Vikram’s assessment of Raj’s new status, while also manipulating Shivani to push Vikram’s property rights toward her. By posing as Sanjana’s boyfriend, Kishen also inadvertently brings Yogi closer to the two women after their fallout, further muddying the trio’s alliance.
Fed up with the destabilization, the three men turn again to Kishen, who drops a coded hint that their enemies might be a single person rather than three separate foes. The men chase Kishen, believing him to be King as Kishen indicates, but their pursuit ends in a disaster when they reach King’s wife Maddy, who—angry at Kishen for flirting with another woman—shoots him repeatedly. They soon discover at his office that Kishen is the true “three-in-one” miscreant in their lives. When Kishen arrives, he is momentarily exposed, but Sanjana intervenes and defends him. In the ensuing tension, Raj announces he will divorce Sanjana, shocking everyone, including Kishen. A few days later, as the three men are drunk, Shivani, Maya and Kishen announce Sanjana’s remarriage; they mistakenly believe the groom is Kishen, creating a chaotic scene that ends with Vikram striking a police officer’s head and the trio being arrested.
While in prison, Raj laments the damage he has caused Sanjana. They are bailed out by King, who offers Raj a pistol to shoot Kishen dead. Vikram and Yogi try to stop him, but Raj fires at Kishen; Sanjana erupts in anger when she discovers Kishen was alive. Raj quickly realizes that the groom wasn’t Kishen but himself, as Kishen reveals that the pistol King gave Raj was real, though the bullets were fake, part of Kishen’s plan to bring Raj to the altar. Shivani, Maya and Trishna press Kishen to reveal what pushed him to such extremes. He opens up about his own past: he was once a womanizer as well, but after his wife Divya committed suicide, he vowed to reform and began devoting himself to helping women in similar predicaments. Sanjana’s memory of Divya fuels his mission, and he explains that his work now is about giving these women a chance to reclaim their lives. With Raj and Sanjana’s renewed bond, Vikram and Shivani begin to heal as well, and Kishen urges Vikram to apologize to Shivani, who ultimately forgives him.
Halfway through the ceremony, Kuku asks Trishna where Kishen is; she hints that he has moved on to help “another Sanjana.” The film closes with Kishen walking away, playing the flute as he wanders the streets, continuing his quiet crusade to mend lives and expose truths that others would rather keep buried.
