Vikram (Sidharth Malhotra) is an acclaimed British writer and NRI. On the night of the launch of his second book in Mumbai, he returns to his hotel to find his wife, Catherine, dead and calls the police. After the police arrives at his place, he evades them and speeds away in his car. While the cops are giving him a chase, his car overturns. He manages to escape with minor injuries and attempts to take shelter in a nearby apartment. Later that night, Maya (Sonakshi Sinha), a young homemaker who resides in the same apartment, spots a police car outside and rushes to it for help. The police enter her flat and find Vikram standing next to the body of her lawyer husband, Shekhar Sinha, whoâ€™s been murdered. The police retrieve a blood-stained candle holder which was the weapon used to kill Shekhar. They also find burnt photographs in the trash can. Dev (Akshaye Khanna), a police officer investigating the double murder case, interrogates both Vikram and Maya.
According to Vikramâ€™s account, he fled from the police because he feared heâ€™d be falsely accused of killing his wife. His wife did not attend the book launch because she was not feeling well, and used to take medicines for a heart ailment. In a nearby apartment, he found Maya at the door of her flat and asked her for help when she was dumping something in the trash can. Vikram entered her flat and found the glass of the center table shattered. Maya told him that she had accidentally dropped a vase on the table. He also noticed that the bedroom door was locked from outside using a key. Maya attempted to seduce Vikram but he did not give in. The doorbell then rang and a tall man entered who Maya introduced to Vikram as her husband. Vikram finds a photo frame in the room and realizes that the man was not her husband but her lover. He attempts to flee but her lover hits him on the head with a candle holder and Vikram momentarily loses consciousness. Vikram gets up later to find her husbandâ€™s body next to him and the police at the door accompanied by Maya.
According to Mayaâ€™s account, her doorbell rang and she answered the door to find Vikram. He was slightly injured and asked her for help. Maya let him in but then found out through the news on TV about Vikram having allegedly murdered his wife. Vikram whipped out a knife and overpowered her. Later, the doorbell rang and it was Mayaâ€™s lover with whom she was having an affair. Since Vikram was standing behind the door with a knife, Maya asked her lover to leave. Around midnight, her husband, Shekhar, returned home and struggled to free her from Vikram. In the struggle, the glass of the center table got shattered and Maya rushed outside to a police vehicle for help. By the time Maya returned with the police, Vikram had killed her husband with a candle holder and was standing next to his body.
The police also interrogate Mayaâ€™s lover who corroborates Mayaâ€™s account. Meanwhile, the police find that a gang rape victim named Sandhya had committed suicide recently because Vikramâ€™s second book had revealed her identity. Examination of Catherine's body reveals that she had died of a heart attack.
The forensic team informs Dev that Shekhar was attacked on the head by someone while Shekhar was standing, and that the attacker must have been at least 6 feet tall. The police initially suspect Vikram as his height is 6â€™1â€. On the second day of investigation, it is found that the photographs that were burnt were those of Maya and her lover, who was also about 6 feet tall. The photographs had been taken by a detective hired by Shekhar. The police eventually conclude that Vikramâ€™s account is true, and that Maya and her lover had killed Shekhar when he confronted them with the photographs. The glass of the center table broke when Shekhar and Mayaâ€™s lover got into a fight, after which Mayaâ€™s lover killed Shekhar by hitting him on the head with a candle holder. They hid his body in the bedroom and burnt the photographs, and then framed Vikram. Vikram is deemed innocent and gets released from custody. He cremates his wifeâ€™s body and is about to fly back to London. Maya and her lover get arrested and are charged with the crime of Shekharâ€™s murder.
At home, Dev is reading Vikramâ€™s second book when Devâ€™s wife (Mandira Bedi) tells him that the protagonist dies of drug overdose in the book. Dev rushes to the forensic doctor to check if Vikramâ€™s wife could have died from an overdose of the medicine she had been taking for a heart ailment. They discover that although the prescription was for a very low dose of the medicine, the pills had been tampered with and the actual dose was four times higher, which would have caused Catherine to have a fatal heart attack.
Dev calls up Vikram while the latter is about to catch a flight to London. On the phone, Vikram confesses to having killed Catherine and Shekhar. He reveals that he killed Catherine because she was threatening to charge him for the suicide of Sandhya. When the police arrived at his place, he noticed a call from Shekhar on Catherineâ€™s phone, who was the lawyer working with Catherine to file a case against him. He then fled to Shekharâ€™s house to retrieve and destroy the legal documents of the case. When Maya went out to seek help, he killed her husband and stumbled across her photographs with her lover while searching for the legal documents. He burnt the photographs and threw them in the trash can, and then created a convincing story to dupe the police. He tells Dev that he has already cremated his wifeâ€™s body so thereâ€™s no evidence left. Dev attempts to stop Vikramâ€™s flight but in vain. Vikramâ€™s voice in the background says that he simply took advantage of a coincidence (Ittefaq) to build his case.