The film opens with Mumbai Police Commissioner Prakash Rathod taking a respite after a jog, describing in a voice-over that he is going to retire from office the following day, and how numerous people have been recently questioning him about the most challenging case he had to deal with in his entire career, and how he has been deliberately evading such questions. As his voice-over ends the film switches into a narrative, showing the events that occurred on a certain Wednesday, which the Commissioner specifically recalls when being asked the said question. An unnamed man is shown to strategically carry a travel bag, assumed to be explosives, in the Chatrapati Shivaji Terminus railway station and proceeding to place the bag, under the false pretense of lodging an FIR, in the toilet of a police station located near the Mumbai Police headquarters. He then arrives on the rooftop of a building under construction where he has set up his base of operations, equipped with various modern technology gadgets and instruments.
He calls up Rathod and informs him that 5 bombs have been placed in different locations throughout Mumbai, which are programmed to explode simultaneously within four hours unless the Commissioner gives in to his demands and releases four militants. In response, Rathod immediately alerts his team involved in intelligence research and surveillance, tapping all the available resources in gathering preliminary information and tracing the location of the caller. Meanwhile, the caller tips off television news reporter Naina Roy, telling her to reach the police headquarters immediately as it is going to be "the most important day of her life". Rathod initially suspects the anonymous caller to be bluffing, but his doubts are dispelled as the caller, to prove his seriousness and the police force's helplessness, reveals that a bomb has been planted in the police station right opposite to the Police headquarters. He tries to trigger the bomb through a cell phone, but it is located in the nick of time and defused, just as Roy reaches the scene on the caller's instructions and reports about the situation.