Suraj Singh Dhillon [Diljit Dosanjh] is a wealthy, eager-to-marry young man who helps run his father Gurnam’s dairy, yet his blunt, raw style often fails to impress potential brides in their arranged-marriage setup. To win over the right match, his friend Sukhi—a filmi buff—urges him to adopt a rebellious, “bad boy” image, echoing bravado seen in popular films. They embark on a chaotic streak of rule-breaking and comic mishaps, all while a private detective named Madhu Mangal Rane [Manoj Bajpayee] quietly records their every move as part of background checks on grooms.
When Suraj and his family meet a new prospective bride, the in-laws flash a photo montage of Suraj’s alleged bad‑boy antics, and the proposal is rejected. Gurnam [Manoj Pahwa] feels humiliated and withdraws from the process. Suraj then tracks down Pandit Dubey [Neeraj Sood], who had previously suggested the arrangement, and learns of Mangal’s involvement. Determined to avenge his family’s dignity, Suraj shifts his focus to Mangal.
Mangal, living a middle-class life with his mother Rekha [Supriya Pilgaonkar] and his sister Tulshi [Fatima Sana Shaikh], becomes the pivotal figure in this clash of generations. Tulshi embodies traditional values in the eyes of the community, making her transformation all the more striking. Suraj and Sukhi reconnoiter Mangal’s office in disguise and, later, raid it late at night. Tulshi, returning from tutoring, stumbles upon the intruders. Sukhi escapes, but Suraj’s coat gets caught in the door, and the two are forced to confront each other. When the family and neighbors gather, Mangal senses Suraj’s intrusion by spotting missing photos and files.
To humiliate Suraj further, Mangal contaminates Suraj’s milk with water the next day. Suraj then recovers a family photo that had been stolen from Mangal’s office, discovering that Tulshi is Mangal’s sister. He pursues her and they end up chatting in a cosmetics store. Having previously damaged her moped, Suraj uses the chance to drop her home and secure her phone number. The following day, he takes her on a date under the pretense of returning the moped, and Tulshi gradually warms to his presence. Meanwhile, Mangal has two suitors lined up for Tulshi, and traditional expectations press her toward one of them.
As their bond deepens, Tulshi reveals her secret life to Suraj: she works as a DJ at a tuition class, a modern persona at odds with the community’s conventional norms. They witness her discotheque persona, and Sukhi sees an opportunity for Suraj to turn the tables on Mangal.
News travels fast: the first suitor backs out after seeing Tulshi’s DJ image in the papers, leaving Mangal stunned and worried about his sister’s future. Tulshi is hurt by the hidden truth, and Suraj’s earnest confession helps win back her trust. Yet the upheaval strains her faith in her brother’s plans. Meanwhile, Mangal crafts a new tactic—proposing Tulshi’s marriage to Suraj with a veneer of social propriety—hoping to seal the match.
On the day of the engagement, Mangal manipulates Gurnam into discussing dowry and records the conversation, leading to the Dhillons’ arrest on dowry charges. Tulshi, consoled by the harsh reality of tradition, seems ready to resign herself to a future determined by others, while Mangal arranges a second suitor as a hurried alternative.
After Suraj earns bail, he uncovers that Mangal is involved with Kavya [Neha Pendse], who is married to the OCD‑leaning mathematics professor Chinmay Godbole [Vijay Raaz]. Seizing on Kavya’s predicament, Suraj presents evidence of the affair to Chinmay and pressures him to file adultery charges against Mangal. Chinmay resists, disillusioned with the courts, but Suraj’s tactics push him toward a louder, messier response. In an attempt to blur the lines of order, Suraj disrupts Chinmay’s carefully arranged life, pushing him to sign the divorce papers.
On Tulshi’s wedding day, Kavya rushes to tell Mangal that Suraj orchestrated the divorce, prompting a moment of reckoning. Realizing his mistake, Mangal apologizes to Tulshi and Rekha, and the trio plans a covert escape to begin anew away from the dowry system. They race toward the railway station, seeking freedom, but Mangal’s desperate act to stop the train—pulling the emergency chain—sparks a chaotic pursuit. Unable to pay the ensuing fines, with the Dhillons unwilling to help, Mangal ends up in jail, and Suraj and Tulshi’s bond remains tested but intact as they lean toward a future together.
