Babumoshai Bandookbaaz begins with giving us a glimpse into the life and times of Babu Bihari (Nawazuddin Siddiqui), a contractual assassin in a certain hinterland of India. "Itna kyun dar rahe ho, ek ko hi marne ke paise milein hain,"- when Babu casually mutters this to an onlooker after bumping off a man, you know he means serious business.
However, one such killing contract causes him to switch loyalties and land a place in the bad books of a local politican Jagat Jiji Sumitra's (Divya Dutta),who is also his regular client. Amidst all this, Babu falls for a village belle Phulwa (Bidita Bag). She sets a condition before him. He has to eliminate two men who had violated her in the past. As expected, the trigger happy Babu sets his blazing gun out and does the deed. Soon, Phulwa moves in with him.
However, things take a murkier turn when Baake Bihari (Jatin Goswami), a fanboy who aspires to be a daredevil hitman like Babu, comes into the picture. What follows next is a tedious ride of flying bullets, fiery desires and hidden motives!