Ajay Rishi Kapoor joins a college in Shimla for further education. He meets Vikram Rakesh Roshan and Nisha Neetu Singh, two laid-back students who adore pulling pranks. Ajay, by contrast, is more serious and becomes an easy target at first, yet he and the two prank-loving friends soon form a bond. Together, the trio begins to stage pranks on unsuspecting people, reveling in clever misdirection and the thrill of getting away with it. One day, they spot a stingy Seth and hatch a plan: they send him a fake typewritten extortion note, hoping to shake down a little money without getting caught.
The next morning, a newspaper reports that the man is dead. Fear sinks in as the trio realizes they could be prime suspects in a murder. They scramble to destroy the incriminating typewriter, only to discover it is missing. A stranger Dev Kumar starts stalking them, heightening the sense that someone is watching their every move. With dwindling faith in the system, Ajay and Nisha resolve to tell the police the truth, even if it seems unbelievable. But before they can come clean, they are stunned to learn that Vikram has been murdered.
Inspector Rajendra Singh Iftekhar enters the scene, skeptical but willing to give them one chance to prove their innocence. Through Vikram’s personal belongings, they uncover a lead—a club singer named Sherie Aruna Irani. Believing she might hold the key to Vikram’s death, they hurry to Sherie’s dressing room after her performance, only to find her dead as well. The young pair deduces that Sherie was entangled in shady dealings and that Vikram was her partner, pulling them deeper into a dangerous web.
As they dig further, they learn that Sherie acted as a middleman between a dreaded criminal known as Black Cobra Kamal Kapoor and those who paid him. Black Cobra is an extortionist, and Vikram appears to have been on his payroll, which suddenly brings many threads into focus. The pieces begin to fit: the Seth’s confrontation, the fake note, and the mounting danger all seem interconnected. Ajay and Nisha deduce that the Seth must have misunderstood the note as being from Black Cobra and confronted him; Cobra’s greed appears to have grown, prompting him to threaten exposure and pull the Seth under his control through fear.
The investigation tightens as they realize Black Cobra believes Vikram and Sherie were secretly extorting people in his name and decides to eliminate them. The killer even steals the typewriter to frame Ajay and Nisha. It becomes clear that someone is following them, either Black Cobra himself or a loyal henchman. Although they lack solid proof about Black Cobra, a crucial clue left by Sherie hints at unmasking him. The stranger confronts them, but the duo manages to overpower him and escape. They bring their findings to Inspector Singh, who arranges to meet them in an abandoned place.
Ajay hands over all the incriminating evidence, but to his shock, the Inspector burns it all and reveals a devastating twist: he is Black Cobra himself. Ajay realizes he has walked straight into the criminal’s trap, and Cobra proclaims that he will kill him and pin the entire series of killings on Ajay. Just when the danger peaks, the stranger bursts in and a struggle ensues, ending with Black Cobra behind bars.
In a final turn, the stranger is revealed to be Charlie, an undercover police officer working on the murder cases. Charlie explains that he had suspected Vikram and Sherie of running the extortion racket long before the first murder and had taken the typewriter to safeguard the truth. Cobra killed Vikram and Sherie to protect his secret, and Charlie had used Ajay and Nisha as part of a larger plan to smoke out Black Cobra. He reassures them that there is no lasting proof against the duo, and he urges them to retrieve the typewriter from him the next day. With the danger behind them for now, Ajay and Nisha vow never to let themselves be drawn into such dangerous pranks again.
