An urban city dweller, Shaurya (Rajkummar Rao) is a simple-living-pure-vegetarian travel agency employee in Mumbai who lives in a shared apartment with a bunch of bachelors. Shaurya and his girlfriend Noorie (Geetanjali Thapa) plan to elope and get married, a day before Noorie's arranged marriage with someone else.

Shaurya currently lives in a boys hostel, so he makes plans to shift to a new flat that will accommodate himself and Noorie. In a hurry to find affordable housing, he ends up moving into a new high rise apartment complex, which is empty due to building and legal issues. The lone security guard stationed at the building is unaware that Shaurya has already moved in, and Noorie also does not know of his new address.

The next morning, Shaurya accidentally locks himself inside the apartment. He makes some initial attempts to break open the lock, but fails. The apartment does not have an electricity connection as yet, and so his phone runs out of battery before he can call for help. Shaurya, now totally disconnected with the outside world, struggles to survive without food, water and electricity. As days pass by, he progressively becomes more claustrophobic, and his attempts to escape becomes more extreme. Desperate for food, Shaurya resorts to eating cockroaches, ants and pigeons, and also starts talking to a rat for company. To his relief it rains heavily and Shaurya collects as much water possible in empty containers. He manages to survive for almost a week, but his physical and mental health starts to deteriorate due to starvation, dehydration and isolation. In a final, desperate attempt to escape, Shaurya begins sawing through the balcony gate with a metal sheet, and ultimately succeeds. He climbs down five floors, almost falling off many times due to exhaustion. He manages to reach a floor which has no balcony gates, and finally escapes the building. Shaurya faints due to weakness and fatigue, and is rushed to the hospital.

One week later, he is visited by Noorie, who reveals that she is now married, since she thought that Shaurya had abandoned her. Heartbroken and traumatized by the incident Shaurya tries to return to his normal life, but he is shattered to see that his friends and colleagues had not even noticed his absence, as they are all too busy in their own world. The whole story is based on how he breaks-free from this deadly concrete cage and ultimately wins over his own demon!