Bombay Police are baffled by a series of crimes - all at the hands of arch-criminal "Black Cat" who leaves his calling card at every scene of the crime. The Commissioner assigns this matter to this best plainclothes agent, Rajan. Rajan's investigations lead him to suspect Professor Gupta, who is also the brother of his girlfriend, Nita. Rajan decides to use Nita's love for him, and spies on Gupta. When Nita finds out, she is enraged at Rajan, and blames the police who she feels are covering-up their inefficiency by making a scape-goat of an innocent man. Rajan fails to prove that Gupta is somehow involved with "Black Cat", and the Commissioner gives him a deadline. If Rajan does not apprehend Black Cat within that deadline, he may be suspended or even dismissed from the police force. With no clues whatsoever as to the whereabouts of Black Cat and it's gang, Rajan has the challenge of his life, which he may not be able to fulfill.