Ek Chatur Naar is a pacy crime thriller set in the town of Lucknow where Mamta (Divya Khossla), a struggling widow stays in the slums along with her son and mother-in-law (Chhaya Kadam). Mamta despite being street-smart who uses her wit and charm to make ends meet, is in huge debt. Her life takes an unexpected turn when she finds the smartphone of a corrupt power broker and a white-collar criminal, Abhishek Verma (Neil Nitin Mukesh), at the metro station where she works. After checking his phone, she finds an obscene video clip of the much-married Abhishek and his girlfriend Tina’s (Heli Daruwala). Mamta tries to con Abhishek for a ransom in exchange of his phone to pay off her debts once and for all. Abhishek engages Inspector Triloki (Sushant Singh) to find his missing phone. How Mamta goes about conning Abhishek in exchange of his phone forms the remaining part of the plot.