Plot
Turkish Interpol officer, Aslan Yilmaz, investigates the assassinations of the Chief Minister of Odisha, the Mayor of France and the Prince of Scotland, where he, with a young Tamil criminologist Judith Samson, deduces that "Cobra", a skilled assassin, is the mastermind behind the assassinations. The duo learn that Cobra perfectly assassinates his targets using mathematical skills, leading them to believe that the master assassin is a mathematics professor. Judith reveals to Aslan that the bullet that killed the Chief Minister ricocheted off a fan, killing him.
Meanwhile, Mathiyazhagan, "Mathi", a mathematics professor revealed to be Cobra, receives his next assignment from his mentor and senior journalist in Kolkata, Nellaiappan. He is to kill the Russian defence minister, Dmitri Yugolsav. He travels to Russia, successfully assassinates him and escapes, despite tight security from Interpol and Aslan's plan that almost trapped him. Before Yugolsav's assassination, Aslan and his team watch a telecast conversation between Nellaiappan and Nawab, who works at a company named Rishi Corporation, where he concludes that the victims are connected to the company's owner, Rajeev Rishi, a psychotic and sadistic business magnate, who inherited the company from his father. Rishi runs a criminal syndicate that targets people who oppose his company. Following the engagement to his criminologist girlfriend and Judith's teacher, Bhavana Menon, Mathi learns that someone has kidnapped Nellaiappan and discovers they are targeting him from the beginning of his assignments.
After a clue from Sudoku, Mathi receives a call from the person, who is Mathi's doppelgänger, and he challenges Mathi to save himself from him. An unexpected turn of events reveals "Mathi" to be Kathirvelan "Kathir", Mathi's schizophrenic long-lost twin brother, and the doppelgänger who challenged Kathir is the real Mathi. Since Mathi killed the cop for insulting their mother, who was hanged after being sentenced to prison for murder, they have been living separately since childhood. Rishi sends men to capture Mathi, but Kathir manages to kill them. Mathi had been holding a grudge against Kathir, as he was responsible for the death of his girlfriend, Jennifer Rosario, who was the daughter of the Kolkata city commissioner Rosario. Jennifer's relatives threw Mathi away on a boat, which reached Thailand, and the police arrested him as a criminal and sentenced him to seven years in prison. Mathi learns about Kathir's identity as Cobra and plans to seek vengeance for Jennifer's death, revealing that he was the one who was sending clues about the assassinations to Interpol.
Mathi hands Kathir to Aslan, where Anand Subramaniam, the investigating officer and Rishi's mole, takes Kathir's help to capture Mathi. Kathir brings them to Mathi's hideout, which is an under-construction mall. Rishi and his men arrive, and a fight ensues between the gang and Kathir, in which he successfully subdues them. Mathi confronts Kathir about Jennifer's death. Kathir reveals that he had arranged for Mathi and Jennifer to leave for Bangladesh, but her father and relatives followed and killed her. After clearing the misunderstanding, Kathir reveals that he killed Jennifer's relatives and locks Mathi in a room. Kathir kills Rishi and his men single-handedly but gets shot and succumbs to his injuries, leaving Mathi and Bhavana devastated.