Raheem and his well-trained pigeon Saara are alone in a coach aboard a train when a blind man enters and reaches an open door. [Raheem] saves the man, but the man turns out to be an assassin and throws Raheem off the moving train to his death. The death is ruled a suicide, but Sangeetha knows that Raheem had no reason to kill himself. The same night, Raheem appears in her dream and says that he was murdered. The following day, Raheem's case is forwarded to the CBCID at Sangeetha's request.
Shiva, Shivalingeshwaran aka Shiva, is a strict CID officer married to a thrill-seeker named Sathya. The couple lives in a house near a cemetery, and Shiva is assigned to Raheem's case and begins the investigation. That same night, Sathya sees a ghost of a child and is frightened, though Shiva cannot see it and suspects she might be imagining things. To help, he brings Pattukunjam, a thief who enters the house as a servant and night watchman. The next day, Shiva visits Raheem's home to investigate Raheem's relationship with his father and Sangeetha, and he suspects Krishnamoorthy is involved because he disapproves of the couple, only to find out that he has nothing to do with the murder.
Sathya's behavior becomes erratic. She roams the city, redecorates the house with green curtains and lights, and cooks biriyani despite no cooking experience. Pattukunjam and other maids report her strange behavior to Shiva. HeConsults his friend and psychiatrist, Ashok, who advises him to quietly observe her. That night, Shiva comes home early, hears a man’s voice and detects the scent of a cigar. He goes to Sathya's room and is shocked to discover that the soul of Raheem has possessed Sathya's body. Raheem warns Shiva that he must solve his murder.
Shiva reviews railway station security footage and realizes the killer was the man posing as a blind person. He tracks the killer down and corners him on a train coach with no passengers. Sathya, still possessed, enters and asks why the man killed Raheem. The killer tries to escape by jumping from the moving train and dies. Shiva takes Sathya to a Darga, informing only Satya's mother about what has happened. Baba helps them exorcise Raheem’s soul, though only temporarily, and tells Shiva that solving Raheem’s case is the only way to save Sathya.
Shiva continues the investigation step by step, aided by Raheem’s pigeon Saara who provides clues. Shiva interrogates Sathya at the CID Conference Hall about Raheem. It is revealed that Raheem recovered Sathya's stolen iPad and returned it to her, though he refuses to reveal his name; Sathya takes a picture of him for posterity. A jealous stalker of Sathya sees this and reports to the residential landline, where Sathya’s father Viswanathan answers and is fed false information that Sathya and Raheem plan to elope and marry. Hearing this, Viswanathan hires [David], an assassin, to injure Raheem.
After exposing the mistaken identity, Raheem’s ghost possesses Sathya and threatens everyone in the hall. Sathya’s father begs for forgiveness, insisting his intent was only to harm Raheem, not kill him. Shiva begs Raheem to release Sathya from the possession and even offers to be the one possessed if it will reveal the killer. It’s revealed that a pigeon-race organizer had hired David to kill Raheem, paying him more money because Raheem and Saara were his rivals in the pigeon race. The organizer is ridiculed by his friends for his incompetence. In the end credits, Shiva and a pregnant Sathya reunite.
