Director: Anees Bazmee
Writer: Rajan Agarwal
Stars: Akshay Kumar as Kishan Khurana, a private detective who specializes in extra-marital affairs; Sanjana’s “boyfriend”, Shivani’s “brother” and Maya’s “friend”
Bobby Deol as Raj Malhotra, Sanjana’s husband, and the primary womanizer of the trio
Sonam Kapoor as Sanjana A. Malhotra, Raj’s wife and Kishan’s “girlfriend”, who seeks Kishan’s help in earning back Raj when she realizes the truth
Irrfan Khan as Vikram Chopra, Shivani’s husband, Raj’s and Yogi’s boss, and the secondary womanizer of the trio
Rimi Sen as Shivani Chopra, Vikram’s wife and Kishan’s “sister”, who seeks Kishan’s help in teaching Vikram a lesson on finding out the truth
Suniel Shetty as Yogi Mathur, Maya’s husband, Raj’s friend and co-worker, Vikram’s employee and friend, and the failing tertiary womanizer of the trio
Celina Jaitly as Maya Mathur, Yogi’s wife and Kishan’s “friend”, who introduces Sanjana to Kishan and has been busting Yogi through Kishan’s help for long
Mukesh Tiwari as King, a dreaded don and Sanjana’s “boyfriend”
Rakhee Tandon as Maddy, King’s wife
Ranjeet as T.T., a veteran don, Maddy’s father and King’s father-in-law
Chahat Khanna as Kanisha “Kuku” Arora, Sanjana’s sister
Smita Jaykar as Tishani Arora, Sanjana’s mother
Shillpi Sharma as Sweety, Yogi’s ex-girlfriend and final extramarital date
Mallika Sherawat in a friendly song appearance as Razia
Vidya Balan in a special appearance as Divya, Kishan’s wife
Raj Malhotra, Vikram Chopra and Yogi Mathur are best friends and business partners who are married to Sanjana, Shivani and Maya respectively, and live in Vancouver, Canada. The three of them constantly cheat on their wives with not one or two but many women. However, while Yogi is the only unsuccessful one due to Maya having a secret friend spying on him, Raj and Vikram are able to get away with their flirtatious behaviour by fooling their wives and keeping them under check.
One day, when the three wives, who are also friends, meet up, and Maya brings up Sanjana’s issue about a free necklace due on Raj when the two met previously that day in a mall, she and Shivani insist on Sanjana having a private detective, Kishan Khurana, Maya’s “friend”, solve the problem. However, when Maya arranges a meeting between them, things don’t seem to work out because Sanjana happens to rubbish away Kishan’s accusations against Raj. This compels Kishan to try exposing Raj by calling all his girlfriends to the New Year’s Eve party, but Kishan’s plan goes haywire when Vikram steps in and saves Raj.
Confused to the next day, Raj and Vikram suspect a spy being part of the scandal that was about to occur last night and seek help from friend and Canadian Security Intelligence Service agent KD, who instead suggests hiring a private detective as the matter is too trivial and unprofessional for an intelligence agency to handle. However, as fate would have it, they land up at Kishan’s place, and, having recognized him from the party, enlist his help. Kishan, who is apparently crushing on Sanjana, decides to engage Raj and Vikram in a double game, which results in the duo mistakenly assuming Yogi as the informer after Kishan shows them a doctored video of Yogi conversing with Sanjana, and ceasing their friendship with him by exposing him on one of his cheat dates. Later that day, he creates a fracas for Raj by nearly exposing him as a cheater when he is caught in a bathing robe, but Vikram again comes up with an idea, this time about having Raj pose as an undercover cop in the CSIS, who was unintentionally exposed during a “mission” for KD, who played his boss, and was responsible for killing dreaded don King’s brother. Sanjana believes the story and forgives Raj, later snubbing Kishan over the exposé.
Realizing that something is wrong with the deal, Kishan learns from Yogi about the plan and decides to expose them by staging himself as King and having them assemble blindfolded, with Sanjana and Shivani in attendance. When the truth is out, Sanjana tries to commit suicide, but Kishan convinces her otherwise, and comes up with a plan to reform Raj and bring his loving former self back to her life, part of which is a plan to entice Raj into jealousy by having Yogi inform him and Vikram of Sanjana beginning an affair and relationship with a dynamic, handsome man, who would be none other than Kishan himself.
Eventually, Kishan’s plan of the jealousy game works out well, but trouble brews big time when Shivani, through Kishan’s help, has Vikram thrown out of the house upon having obtained ownership of all his property by getting him to unsuspectingly sign “bank account” papers during the time he was advising a troubled Raj, who made a witness. Helpless and destroyed, the three men turn to Kishan for help again, where they request him to blow the covers of their enemies, and vow to batter their fugitives to death, little knowing that they instead have a common enemy in Kishan, who throws a subtle suggestion about the same which they fail to recognize, and while Sanjana is to keep a fast for Raj, Kishan comes up with his own plan and lures the trio to King’s house after they end up with his jacket. Kishan then arranges the trio to meet King’s wife Maddy, who too is doubting King’s possible affair, but the meeting turns out a disaster when they learn that King is innocent and Maddy starts shooting at King left, right and center for flirting with another girl.
While waiting for him at his office to discuss details of the meeting, Raj and Vikram, along with Yogi, finally figure out in a sudden fit of musical epiphany that Kishan was in on the scam, double-crossing the three men while playing for their wives, posing as Sanjana’s boyfriend, Shivani’s “brother”, and Maya’s “friend”, having lured them to King’s lair out of intent. Sanjana disrupts a fight about to break between the four after Kishan arrives to find himself exposed. Assuming her to be openly in league and love with Kishan, Raj demands a divorce from Sanjana, and a shocked Kishan, in the next few days, manages to convince a crying Sanjana for marriage. However, while trying to invite the trio, Kishan is mistaken as the groom-to-be, and they, drunk, are arrested for smashing a police officer’s head.
While in the cell, Raj rues about Sanjana and contemplates deceiving her, when he, Vikram and Yogi are bailed out by an injured King. Raj is in fury and decides to kill Kishan, for which King has his henchman Benny give him a gun. Raj succeeds, but when Sanjana confronts him, it turns out that the assembly of people was for the couple’s remarriage. However, Kishan reveals himself to be alive, giving the wives relief, with King and Maddy showing up, as Kishan had arranged for their bail. Seeing his dedication, the wives, and Sanjana’s mother and sister, ask Kishan about his reason for helping Sanjana way too personally, something which is unexpected of a professional of his kind. Kishan then reveals that his wife Divya once walked in on him cheating on her and committed suicide by slitting her wrist. Feeling guilty and breaking down, he set off on a mission to help aggrieved ladies of his wife’s kind in order to redeem himself. However, it was with Sanjana that he saw a reflection of his wife in her, and decided to help her by any means necessary.
Finally, everything patches up with the three couples reuniting, while Kishan leaves Vancouver for his next mission.