Avantika Ahuja (Kareena Kapoor) who lives in the US returns to Delhi after her father has a cardiac arrest. While in Delhi she meets Ehsaan Khan (Saif Ali Khan), a Delhi University Professor. Being in the same profession at the same place love blossoms between the two. Meanwhile Avantika gets a return call from New York asking her to rejoin her job. She breaks this news to Ehsaan and expresses her desire to work in the US, Ehsaan agrees and joins her but before that Avantika's father has some reservations about her daughter marrying a Muslim.However he gives in as the couple has decided to get married. Eventually they get married and move to the USA. Avantika helps Ehsaan in getting a job at the same university where she teaches and Ehsaan is appointed as a professor to teach Islam and the Modern World. Avantika's life changes when her neighbor Salma (Nauheed Cyrusi) informs her about her house arrest and requests Avantika to help her by contacting her friend Rihana (Dia Mirza), a TV reporter. Avantika meets Rihana and tells her about Salma's problem and meanwhile she meets Riyaz (Vivek Oberoi), Rihana's boyfriend and colleague who takes Salma's problem as a case of domestic violence. Unfortunately Rihana has to fly out of the city before meeting Salma and she gets her flight information when Avantika is still at her office. Avantika becomes pregnant and waits at her house to share this with Ehsaan but when she hears voices coming from their neighbor's house, she investigates and finds out that her neighbors Bhaijaan (Om Puri) and the others are planning to blast the flight in which Rihana is traveling, and have also killed Salma as she wanted to expose them. Her neighbors see her and chase her to her house where she meets Ehsaan who consoles her but soon reveals that he is also a part of the terrorist group. Bhaijaan ask Ehsaan to kill her in order to make their operation successful however Ehsaan denies after learning that Avantika is pregnant. Ehsaan keeps Avantika in house arrest and threatens to kill her father in India if she tries to inform anyone. Avantika realizes that she is a pawn in Ehsaan’s game. It turns out he married her to legitimately obtain Social Security Cards and a new identity in the USA. Avantika calls Rihana and leaves a voice message on her office number to stop her from boarding the flight but it was too late. The plane explodes killing Rihana and all others on the flight.