An aspiring filmmaker named Yogita is in the midst of shooting a documentary about the acclaimed director Anurag Kashyap. During a MAMI event, both Kashyap and the legendary actor Anil Kapoor are interviewed by Sucharita Tyagi. Anil expresses his desire to collaborate with Anurag on a film, but Anurag brushes off the suggestion, harboring resentment for being overlooked by Anil when he was just an emerging talent. Now, the tables have turned; Anil's star power has waned while Anurag is now a sought-after director.
The tension escalates when an audience member poses a provocative question: who is more critical to a film's success, the director or the actor? Their heated argument spirals into personal jabs about their respective careers, culminating in Anurag throwing a glass of water in Anil's face, a scandal that tarnishes Anurag's reputation within the industry, leading several film personalities to distance themselves from him.
The narrative takes root in 2007 when Anurag had approached Anil with the opportunity to star in "Allwyn Kalicharan," an offer that Anil declined without a second thought—an act that Anurag has carried with him ever since. Fast forward to the present, still fuming in his room, Anurag is inspired by Yogita's insight.
On Christmas Eve, coinciding with Kapoor's birthday, Kashyap enlists Yogita for a new story about a crazed director who kidnaps an aging actor's daughter. However, Anil keeps Anurag waiting for three hours, initially mistaking the meeting for a prank. When Anurag reveals that they’re indeed filming, where Anil is the protagonist and Anurag takes on the antagonist’s role, reality hits hard.
In a shocking twist, Anil discovers that his own daughter, Sonam, has been kidnapped by Anurag in a bid to capture authentic reactions during Anil's frantic search for her. Anurag, now in possession of Sonam's phone, sets ominous parameters: Anil has only ten hours until sunrise to locate his daughter, with four strict rules: no outside help, no police involvement, all calls must be on speaker, and Yogita's camera must remain recording.
Anil's instinct is to reach out to the authorities, but Kashyap manages to convince the police that it’s merely a part of their film rehearsals, leaving Anil feeling utterly helpless. His attempts to verify Sonam's alleged abduction grow increasingly desperate, especially after Anurag shows him live footage of her being threatened by a masked man.
Realizing she was last seen at a hotel, Anil uses his influence to obtain CCTV footage that reveals the identity of the getaway driver. Despite his best efforts roaming the streets, he finds little evidence against the driver. As the clock ticks down, he returns home where his family is celebrating his birthday. Anil stealthily seeks assistance from his son Harshvardhan, but this risks alerting Kashyap.
In a dramatic twist, Anil confronts Anurag, escalating tensions to violence as Sonam's dire fate looms larger. Anurag, committed to his narrative, gives Anil just seven hours to prove he remains the hero he claims to be. With time rapidly dwindling, Anil’s relentless pursuit finally leads him to a Christmas gala where, for the price of a luxurious watch, he learns the getaway driver's whereabouts.
As the pressure mounts, Anil confronts the driver, only to face tragedy when he gets struck by a car. Bloodied and broken, he reveals his deep regrets before the camera, capturing his anguish as a father. Anurag, exploiting Anil's vulnerability, appears to instigate further chaos.
In a shocking turn, the story reveals segments of Anurag's own script which manipulate the events at hand. After a prolonged chase, they discover details about Sonam's captor and the location of the kidnapping, leading to a harrowing final act as they confront Kashyap’s intricate web of deceit.
Just as day breaks, tension escalates to a boiling point when Anil accidentally shoots Kashyap while demanding answers. In the aftermath, a deeper conspiracy unravels, exposing that Anil had meticulously orchestrated this elaborate plot alongside his family, aiming to use the scenario for a comeback.
Kashyap finds himself facing justice, receiving a prison sentence for the series of events that unfolded. Meanwhile, Anil is vindicated, having acted in self-defense despite the drama surrounding his decision-making.
Months later, the fallout results in a successful film titled "Once Upon A Time in Bollywood," which garners accolades for both Yogita as a director and Anil Kapoor for his compelling performance, while Kashyap, now confined to a mental asylum, begins plotting his revenge from within.
