In 2010, Thenmozhi, a carefree girl from Chennai, comes to Boston to meet her new-born niece. Three weeks later, while leaving for Chennai, in the airport, she gets a free upgrade to first class. During the flight, she starts vomiting due to overeating, and with her co-passenger Sathyadev help, she feels better, and develops a crush on him. The next day in Chennai, Sathyadev and Thenmozhi meet at a cafe, when a gangster named Victor Manoharan comes with his gang to abduct Thenmozhi, but fails due to Sathya's intervention.

Past: In 1986, Sathya's father is killed by a gangster, after which the 16-year-old Sathya makes a decision. In 2002, Sathya is seen in prison with Victor where he fights along Victor on a botched attempt to kill the latter. They escape from prison, and Sathya arranges Victor married to his love interest Elizabeth aka Lisa. Sathya and Victor meet an illegal organ dealer named Matthew where Sathya infiltrates the gang, revealing himself as IPS of Tamil Nadu Police Department Crime Branch. Sathya kills Matthew and engages in combat with Victor and shoots him on his shoulder, to which the latter swears vengeance on Sathya.

2 years later, in an attempt to nab a gangster in Egmore Railway Station, he helps a pregnant woman named Hemanika, who needs to get to a hospital urgently for delivery. Two years later, Sathya again meets Hemanika and her child Isha. After meeting and knowing about each other over the course of 3 years, they decide to get married. On the eve of their marriage, Hemanika is brutally murdered, which leaves Sathya heartbroken, but Isha is saved as she was with him that night. Sathya meets and kills his adversary Golden Raj, but learns that Raj did not kill Hemanika. Sathya hides the fact from Isha by telling her that Hemanika had left somewhere far away and she wanted him to take care of her where he decides to quit his job and travels with Isha around India, along with his colleague DCP Richard's help.

Sathya returns to Chennai after 6 years, where he learns that his friend Kandha's 15-year-old daughter Niranjana has gone missing. He discovers that Victor has resurfaced and is stealing organs illegally with foreign doctors to earn millions, and is trying to save his new customer, billionaire Muruganandham who needs a heart transplant. Sathya is able to find the child and eventually the organ theft network's next target, Thenmozhi. Sathya is reinstated into the police department and leaves for Boston.

Present: Sathya lets Thenmozhi stay in their house with Isha. In an attempt to get Thenmozhi, Victor and his team kidnap Isha, who is held captive by Lisa. Victor tells Sathya that he will release Isha only if he surrenders Thenmozhi, to which Sathya accepts. When they arrive at the location, they kill Muruganandham. Sathya finds Thenmozhi's location, and leaves to find Isha, who is held at knifepoint by Lisa and attempts to stab Isha which makes Sathya to shoot and kill her, which leaves Victor heartbroken.

Victor sneaks into Sathya's house, kills all the policemen positioned on Sathya's house and reveals himself as Hemanika's killer. The duo engages in a bloody fight with Sathya victorious; he slashes Victor like how Victor did to Hemanika, he drags a wounded Victor outside and leaves his colleagues to kill him. Isha and Thenmozhi plan out the former's birthday. Thenmozhi promises to be with Isha throughout the day. Before Sathya takes Isha home, he reminds Thenmozhi of the pending coffee that Thenmozhi wanted to have with Sathya, indicating that he is ready to move on with Thenmozhi.