Four friends, who have accidentally committed crimes, decide to loot Rs. 20 crore, posing as cops. But on the way, they encounter a real police inspector, who orders them to do an encounter.
The story of the film revolves around 4 cops Pankaj Suri aka SIR (Naseeruddin Shah), Albert Pinto aka PINTO (KK Menon), Balvinder Singh aka BOBBY (Atul Kulkarni) and Shakti Chinappa aka SHAKTI (Ravi Kishan); who see an opportunity for a great future when they are given a mission to pull off. Things take a twist when another cop stops their van en-route and takes them as his backup to catch a dangerous gangster.
The story unfolds through the night where the fine line between law and crime is repeatedly crossed, leading to unexpected situations, sometimes very hilarious. The 4 guys who think of themselves as very rough and tough, macho men encounter situations where they are forced to reckon with a different truth about themselves.
Exploring a humour crime genre, Chaalis Chauraasi is like a rollercoaster ride in an amusement park, except that it takes place in a police van.