Indian Army Chief COAS General Pratap Malik (Vikram Gokhale) authorizes the formation of a covert Secret Operations unit DSD (Data Systems Diagnostics), a classified off the books intelligence Unit, directly under Army Chief's control, capable of going on clandestine missions and operations behind enemy lines. He selects Colonel Abhay Singh (Manoj Bajpayee) to command the unit. Abhay Singh chooses seven Army Officers for this new unit. Maj. Jai Bakshi (Sidharth Malhotra), Lt.Col Anees and Capt. Maya Semwal (Pooja Chopra) is his first recruits. Over the years, Abhay along with his unit conducted several successful high-profile covert operations in various parts of the world.
One day while conducting Telephone surveillance in South Block, New Delhi, Jai overhears a representative of Indian Arms lobby Lt.Gen Gurinder Singh (Retd) (Kumud Mishra), an ex-Army officer, attempting to bribe the Army chief, on behalf of a Czech firm, with a USD $2.5 Mn offer. The Army Chief flatly refuses and rebuffs the offer. This angers Gurinder, who in turn, reveals that he is well aware of DSD's existence and its functioning and before leaving, threatens to expose it to the general public. This alarms the Army Chief who immediately contacts the Defence Minister and informs about a foreign Military-Industrial nexus trying to influence the Indian Arms' Market through Gurinder Singh. The Defence Minister, however, refuses to intervene, leaving the Army Chief to deal with them himself. He, however, warns the Army Chief about the possible repercussions, should the existence of DSD become a public knowledge.
Meanwhile, Jai, while listening to all this suspects a major scam involving the Indian Army. He conducts several more illegal Telephone Surveillance missions, in addition to those authorized by Abhay Singh, so as to get the full picture. After 2 months of continuous surveillance, Jai goes rogue. He along with his new girlfriend Sonia, a cyber-expert (Rakul Preet Singh), escape India and head to London, carrying along with him, a highly sensitive data.
Capt. Maya informs Abhay about Jai going rogue and the theft of highly sensitive data from the DSD Office. Abhay activates his intelligence network and launches a manhunt for Jai. Through his sources, Abhay comes to know about Jai's plan of leaving along with Sonia. He raids Jai's house but doesn't find anything worthwhile, even Jai's mother is completely unaware of him going rogue.
All this while, a corrupt Army Officer Brig. K Srinivas, spies on Abhay's movements and keeps reporting them to Gen Gurinder. Abhay, however, outsmarts Srinivas and successfully manages to escape. DSD meanwhile shift their office to an undisclosed location, abandoning their existing Office.
Lt.Gen Gurinder Singh, seeing his plan of capturing Abhay fail, contacts an influential journalist. He provides her with sensitive information, exposing Army's secrets and asks her to run a smear campaign against the current Army Chief along with giving a good PR to the next Army Chief.
While all this is going on, Gen. Malik personally meets Abhay and informs about the termination of DSD, Foreign involvement in Indian Defence Deals and Lt.Gen Gurinder Singh's involvement with a powerful London based Arms dealer Mukesh Kapoor (Adil Hussain), who's the major culprit behind all this fiasco. General Malik further informs Abhay that once the information about DSD goes public, Abhay will be declared a traitor and thrown out of the Army, along with his team.
Abhay, however, remains unperturbed and promises Gen. Malik, that he will expose the wrongdoings and punish all those involved in the scam so as to protect the integrity of Indian Army. After the meeting, with Srinivas still tracking him, Abhay heads to the DSD office, where he informs his team that they have been disavowed, with Government denying their existence. Abhay and Maya alert all their sources and order them to keep a low profile, so as to avoid detection. While this is going on, Jai calls Abhay and they end up having a war of words, with Jai warning Abhay to leave everything and run and Abhay labeling Jai, a coward and a traitor.
At that very moment, Brig. Srinivas makes his move but fails to capture the DSD and its members. Abhay flies off to London, in pursuit of Jai, while DSD members stay back in India.
In London, Jai calls and threatens Gurinder in renegotiating a deal, revealing that he has bugged Gurinder's house. The frightened Gurinder reluctantly agrees and transfers the money to Jai's account. Abhay, in the meanwhile, has also reached London. He contacts a London-based immigrant Tariq Bhai (Anupam Kher), who is known to be a middle-man for Intelligence agents. Tariq Bhai and Abhay attempt to locate Jai and Sonia but fail. However, their activities alert Jai, who orders them to back off, but Abhay refuses and instead vows to hunt him down.
Finally, out of desperation, Abhay contacts Mukesh Kapoor and fixes a meeting with him. At the same time, Jai also fixes a meeting with a few MI-6 Officers. Abhay reveals to Mukesh that Jai possesses sensitive incriminating data, which can badly affect his business and therefore asks Mukesh to eliminate Jai. Mukesh, however, is suspicious of Abhay but is forced to accept the offer, when Abhay reveals his knowledge of Mukesh's identity as that of an ex Indian Army Colonel and the capture of Gurinder Singh by DSD.
However, Abhay double crosses Mukesh by informing Sonia about the threat to Jai's life and orders her to lure Jai to an undisclosed location. Jai's meeting ends up in a shootout with 2 MI-6 agents getting killed and he himself getting wounded. Jai, however, makes it to the place, where Abhay and Sonia are waiting for him.
Abhay, on seeing Jai, severely beats him and derides him as a traitor. Jai, however, justifies his actions and accuses the Indian system of harboring corrupt and eliminating those who raise a voice against corruption. Abhay mocks Jai's justification, by calling it a lame excuse and insults his generation, but Jai counters this by stating that it was the older generation who was responsible for the massive corruption in India. Jai further questions the legacy that the older generation plans to leave for the youth, thus forcing Abhay to agree with him.
Meanwhile, Mukesh, angry at being fooled, takes Tariq Bhai hostage and plans to execute him, but is forced to stop when Jai informs him that he will surrender all the sensitive information regarding Mukesh Kapoor's deals and requests for a personal meeting. Mukesh, realizing that Abhay still has Gurinder Singh, reluctantly agrees. Jai informs Abhay about a major Army housing scam in Mumbai, involving Gurinder Singh and the Defence Minister. He further tells that the only eyewitness to the entire scam, a watchman named Baburao Shastri (Naseeruddin Shah) is being hidden by Jai in a small hotel in Paharganj, Delhi.
Abhay immediately heads back to India and meets Baburao, who confesses to him, about the irregularities in a major Army housing project in Colaba, Mumbai and the involvement of several senior bureaucrats and Army Officers lead by Gurinder Singh. Abhay records Baburao's confessions and gives them to the same influential journalist who earlier had met Gurinder Singh. The journalist is revealed to be Abhay Singh's ex-girlfriend, who tells him that she plans to run Gurinder's story tomorrow. Abhay gives her Baburao's confession and requests her to listen to both the stories and run the story which she finds fit. The journalist listens to both the stories and decides to run Abhay's story, thus deciding to expose the Army's housing scam.
Meanwhile, Brig. Srinivas finally captures all the DSD members and frees a captured Gurinder Singh. But it is of no use as the DSD is absolved of all the crimes and Army's Housing scam gets exposed. Gurinder Singh, overcome with shame and guilt, shoots himself dead.In the ending scene, Jai pays a final visit to Abhay before vanishing for good and Abhay is shown performing his duties as usual.