Vikram, portrayed by Sidharth Malhotra, is a recognized NRI writer from Britain. On the evening of his second book launch in Mumbai, he returns to his hotel to find his wife, Catherine, dead. In a panic, he contacts the police but quickly evades them, fleeing in his car. However, during the chase, his vehicle flips over, leaving him with minor injuries. Seeking refuge, he finds himself in a nearby apartment.
Meanwhile, Maya, a young homemaker played by Sonakshi Sinha, notices the commotion outside and rushes to a police car for assistance. When the police enter her home, they discover Vikram standing near the lifeless body of her husband, Shekhar Sinha, who has also been murdered. A bloodied candle holder is recovered, identified as the weapon used in Shekhar's death, alongside burnt photographs found in the trash.
Detective Dev, portrayed by Akshaye Khanna, is assigned to investigate this double homicide. He questions both Vikram and Maya. Vikram explains that he fled because he feared being wrongfully charged with his wife's murder. He claims Catherine missed the book launch due to a heart condition. In his frantic escape, he had encountered Maya, who was discarding something in her trash can. He noticed her apartment's center table was shattered and that the bedroom door was locked from the outside. Despite Maya's attempts to seduce him, the situation escalated when her lover unexpectedly arrived, and he was struck by the candle holder, losing consciousness momentarily.
On the other hand, Maya recounts how Vikram, injured and seeking help, entered her apartment. As they discussed the unfolding news of the alleged murder, her lover arrived, prompting Maya to shield him from Vikram in a tense standoff. The confrontation becomes lethal when Shekhar returns home and struggles to defend Maya. Ultimately, Vikram is found standing next to Shekhar's corpse when the police arrive.
As the investigation deepens, Maya's lover confirms her account. Additionally, it is revealed that a gang-related incident led to the suicide of Sandhya, which Vikram's latest book exposed. Autopsy results indicate Catherine died from a heart attack, complicating suspicions surrounding Vikram.
Forensic evidence initially points to Vikram due to his height, as the attacker is estimated to be over six feet tall. However, as more details emerge, including the burned photographs of Maya and her lover, the narrative shifts. It becomes evident that Shekhar confronted them about the affair, leading to a violent altercation resulting in his death. Vikram is eventually exonerated and released from custody.
As Vikram prepares to return to London after cremating Catherine, Detective Dev discovers troubling details about her demise. With a revelation that the medication she took had been tampered with, enhancing the dosage to a fatal level, Dev understands the full extent of the tragedy.
In a shocking twist, Vikram confesses to Dev during a phone call just before boarding his flight. He admits to having killed both Catherine and Shekhar, motivated by threats regarding a case involving Sandhya's suicide. In a cleverly devised plan, he manipulated the events surrounding the murders to evade justice, ultimately proclaiming how he exploited the situation, which he refers to as Ittefaq.
