Irfan Ahmed, an IIT Madras gold medalist based in Triplicane, Chennai, lives with his friends and mother, Praveena Begum, a Sub-Inspector of Police. He is in a relationship with Archana Krishnamoorthy, who is doing her Ph.D. in Delhi, and also befriends a junior lawyer, Prathana Raman. Irfan unsuccessfully attends job interviews, while working part-time with a perfume factory. Tired of being questioned on his religious beliefs during interviews, Irfan decides to join a full-time perfume business, which is headed by Perumal and his son, Karthikeyan. He visits various locations in the country to shop for chemicals. On his way back from Hyderabad, Irfan loses his cellphone.

Frustrated that he might miss his flight to Chennai, Irfan mistakenly threatens the airport officials that he will bomb Hyderabad, which leads to his arrest, but is released and reaches Chennai. Later, a bomb explodes at the same airport, killing many people. The next day, Irfan's phone is found at the bomb blast site, and Irfan is arrested, yet again. He is detained under the orders of NIA advisor, Ajay Dewan. He is interrogated by NIA officer, Anisha Qureshi, and low-ranking police officer, Gunashekhar. Irfan is believed to be the most wanted terrorist, dubbed Abu Bakr Abdullah. As a result, he is branded as a terrorist and portrayed as the evil incarnate by the media, and undergoes torture under police custody.

Feeling sorry for Irfan, Prathana decides to represent him and brings Praveena Begum to see him. However, they are denied to visit Irfan. Being an asthmatic patient, Praveena collapses from an attack, due to the humiliation stemming from the public prosecution. Irfan is granted to visit his mother in the hospital, under extreme surveillance of the police. However, he escapes from police custody and finds that Praveena Begum has died, leaving Irfan devastated and escaping from the hospital, where he is met by Dr. Zazi's son Riyaz, who convinces and motivates Irfan to create a sarin gas, to pull off a terrorist attack. Irfan does so, which is eventually tested on Dr. Zazi, when he visits the factory and is shocked to see what was going on.

Anisha reaches there and surrounds Irfan and Riyaz, but is stabbed by Karthikeyan, who is revealed to be the real Abu Bakr Abdullah. When the bomb is activated, Abu Bakr activates the bomb and tells his henchman to kill Irfan, as he has no use of him, but Irfan overpowers and kills the henchman, where it is revealed that Irfan is actually an undercover NIA agent and waited for years to draw Abu Bakr out of hiding. Archana, who is also an undercover NIA agent, arrives at the factory and finishes off Riyaz, while Irfan kills Abu Bakr. Gunashekhar and the cops surround the factory, under the orders of Ajay Dewan. After getting permission from the Defense Minister, a government-sanctioned drone, fires a military missile to the factory.

Archana tries to persuade Irfan to leave the factory, as it is about to be destroyed. However, he refuses, as he wants to stop the activation of the sarin gas. The factory is destroyed by the missile, seemingly killing Irfan. Ajay Dewan is congratulated for preventing the gas attack. It is revealed that the whole operation was planned by Ajay Dewan, which was only known to very few people. He found an officer with a chemical engineering background and named him Irfan Ahmed, erasing his past life. With the help of Archana, Irfan eliminates Abu Bakr's chemical engineerAshraf, in order to lure Abu Bakr to India. It is also revealed that Irfan actually escaped from the missile strike of the factory and is on another mission, where his real name is revealed to be Faizal Ibrahim Raiz (FIR).