As Chatur Ramalingam returns to India with a crucial business deal on the horizon, he reunites with his old college buddies, Farhan Qureshi and Raju Rastogi, in the charming town of Shimla. Their nostalgic reflections on their days at the Imperial College of Engineering bring back vivid memories of Rancho, a free-spirited learner who often clashed with the stern Dr. Viru Sahastrabuddhe ("Virus").
Even in their college days, Rancho's defiance was apparent as he fought for Joy Lobo's right to graduate, despite Virus's relentless opposition. The unfortunate events that followed prompted Rancho to confront Virus regarding the excessive pressure placed on students, but Virus, steadfast in his convictions, remained unyielding. This crucial confrontation marked a significant turning point in Rancho’s relationships with his peers.
Fast-forward to the present, and the trio—Rancho, Farhan, and Raju—crash a wedding, only to discover that it's the celebration of Virus's daughter, Mona. To their surprise, they are interrupting her wedding to the materialistic Suhas, whose shallow nature is later exposed by Rancho's candid remarks. Pia, Mona's younger sister, initially heartbroken over Suhas's departure, finds solace and reassurance in Rancho's unorthodox outlook on life.
Tensions escalate when Virus warns Farhan and Raju to distance themselves from Rancho, which leads Raju to seek comfort with Chatur, a diligent student known for his rote memorization techniques. Fueled by their rivalry, Rancho and Farhan play a prank on Chatur by altering his Hindi speech, leading to an embarrassing yet humorous outcome that ignites a competitive spirit among them. Chatur, furious, challenges them to a contest: whoever achieves more success in ten years will be the real champion.
As exams loom, tragedy strikes when Raju's father experiences a heart attack, prompting a rapid response from Rancho and Pia, who manage to save him in the nick of time. This act of heroism spurs a series of events that culminate in Virus making a bold wager: declaring that neither Farhan nor Raju will find a job after graduation.
As pressure mounts, Rancho encourages his friends to confront their true passions and desires. Farhan reveals his love for photography over engineering, while Raju grapples with feelings of inadequacy. This newfound clarity fosters a pact: if Rancho confesses his feelings for Pia, they will collectively confront their individual challenges.
In a moment of drunken revelry, the friends embark on a midnight visit to Virus’s home, leaving their marks along the way. However, the intrusion is cut short when Virus catches Raju at his doorstep, threatening to either expel him or expose Rancho's secrets. Faced with this dilemma, Raju attempts suicide but survives miraculously, prompting Virus to reconsider the expulsion ultimatum. In a turn of fate, Raju manages to secure a job, while Farhan persuades his father to support his photographic ambitions.
Ultimately, Rancho's presence makes a profound impact, empowering his friends to face their fears and achieve success on their own terms. As Virus seeks revenge against Raju for his recent triumphs by constructing an arduous exam, the tables turn when Rancho and Farhan, with Pia's subtle aid, manage to filch the test paper. Yet, Raju exhibits admirable integrity, opting to discard the stolen paper rather than cheat, even when faced with the consequences.
As a tumultuous night unfolds, Mona goes into labor, and with the help of Rancho, Farhan, and Raju, she brings new life into the world. Virus, recognizing Rancho's unwavering commitment, gifts him a Space pen as a token of respect. However, on graduation day, Rancho mysteriously disappears, leaving nothing but whispered memories of his presence.
In the present, Farhan, Raju, and Chatur embark on a quest to uncover the truth about their long-lost friend, leading them back to Shimla. There, they are met with an astonishing revelation: the true Rancho was never who they believed him to be. Instead, he was the gardener's son, Chhote, who adopted Rancho's identity to pursue education. Their journey takes them to Manali, where they disrupt Pia's impending wedding to Suhas, urging her to join their mission.
Their adventures ultimately lead them to a remote area in Ladakh, where they discover a school run by none other than their friend now known as Phunsukh Wangdu. Initially dismissive of Rancho’s essence, Chatur’s perception is shattered when he realizes that Phunsukh Wangdu is not just the true Rancho but also an esteemed scientist and entrepreneur. Faced with this revelation, Chatur begrudgingly acknowledges his defeat, and the friends celebrate their joyous discovery together.
