Woody Grant, portrayed by Bruce Dern, is discovered wandering through the streets of Billings, Montana, when a police officer intervenes. His son, David, played by Will Forte, picks him up and learns that Woody is determined to travel to Lincoln, Nebraska, to claim a supposed $1 million sweepstakes prize he believes he has won. However, when David examines the announcement, he quickly realizes it's merely a deceptive mail scam aimed at encouraging magazine subscriptions. After returning Woody to their home, David's mother, Kate (June Squibb), expresses her frustration over Woody's obsession with the nonexistent money, which affects David’s work as a stereo salesman.
Their discussion about Woody’s well-being leads David and his brother Ross (Bob Odenkirk), a local news reporter, to consider taking him to a retirement facility. David also encounters his ex-girlfriend, Noel, who is in the process of returning his belongings and declines his offer to rekindle their relationship. Suddenly, Kate calls to inform David that Woody has gone missing again, prompting David to retrieve him and ultimately decide to drive to Lincoln, much to Kate's discontent.
While en route, the pair experience a detour when Woody vanishes and indulges in drinking. After a night of debauchery, he returns to their hotel, only to fall and injure himself. Following this incident, David takes Woody to the hospital, where they discover that Woody has lost his dentures. They eventually track down the lost dentures at a train station, and Woody nonchalantly re-inserts them. During Woody's hospital stay, David informs the family about the situation, leading to the planning of a reunion in Woody's hometown.
Upon their arrival in Hawthorne, Nebraska, they enjoy lunch with Woody’s brother Ray (Rance Howard) and his relatives. David and Woody reminisce with family members, visit a mechanic shop that Woody once owned, and stop by a local bar. Tensions rise when Woody openly discusses his past issues with alcohol and his feelings of indifference towards his family. An argument ensues, causing Woody to storm off. Afterward, they stumble upon Woody's old business partner, Ed Pegram (Stacy Keach), whose presence brings back old grievances—the family harbors resentment against Ed for allegedly stealing Woody's air compressor years prior.
Fueled by excitement, Woody foolishly flaunts his supposed winnings, prompting patrons at the bar to toast him. When news of Woody's "fortune" spreads overnight, they seek out Woody's wife Kate to join the reunion, and she takes them to the cemetery to honor family members from the past, sharing some intriguing anecdotes about Woody's lineage and their history.
During dinner, Ed, now a karaoke performer, disrupts the evening by bringing attention to Woody's presence. In a subsequent restroom encounter, David learns from Ed about a loan Woody owes him, garnished with veiled threats of legal consequences. David's interactions expand as he meets the local newspaper editor, who, in addition to planning a story about Woody, shares insights about his father's past and experiences after serving in the Korean War.
Relatives visit Woody, bringing further complications to family dynamics, and when they unexpectedly ask for money they believe Woody owes them, tempers flare. Kate intervenes, exposing the debts that those relatives owe to Woody. They embark on a tour of Woody's dilapidated childhood home, and in a fit of mischief, David and Ross attempt to reclaim the air compressor from Ed, only to make a blunder when they mistake another house for Ed's.
Later that night at the bar, after a drunken outing, Woody's past indiscretions resurface when Ed mentions Woody's infidelity before David's birth, leading to an emotionally charged confrontation. The night spirals when Bart and Cole, Woody’s nephews, rob David of the important sweepstakes letter, only to later reveal their disdain for both Woody and David. In their search for the letter, they discover Ed has it, reading it aloud to humiliate Woody at the bar.
Ultimately, Woody fights to reclaim his pride by getting the letter back, and an altercation with Ed leaves David feeling protective of his father. When Woody expresses a desire to use the “winnings” to buy a truck, David, realizing the impracticality given Woody can no longer drive, convinces Woody to postpone their journey to Lincoln. Yet, Woody's determination continues as he sneaks out for another attempt, prompting David to relent and accompany him.
Arriving at the marketing agency to claim their "fortune," they are deflated upon learning that Woody was never the prize winner. However, as a parting gift, Woody receives a consolation prize hat. Before departing Lincoln, David makes a sacrifice, selling his car to purchase Woody a truck along with a new air compressor. They celebrate their bond by driving the truck along Hawthorne’s streets, sharing formative moments with friends and family, including an old flame of Woody's, an incredulous Ed nursing his black eye, and Woody's brother Albert, whom he waves goodbye to. In a poignant moment, they switch driver’s seats, with Woody feeling the thrill of the road while David drives them back home.
