William Tell, portrayed by Oscar Isaac, is a skilled gambler who honed his card-counting skills during an extensive eight-year imprisonment. With a desire to live under the radar and evade casino security, his approach to gambling is characterized by small bets and modest wins. Remarkably, he opts to stay in motels, traveling light with just two small suitcases, and he goes to great lengths to strip the rooms of any personality by covering the furniture with plain sheets tied down with twine.
During a casino visit, Tell crosses paths with La Linda, a familiar figure from the gambling circuit, played by Tiffany Haddish. La Linda manages a group of investors who provide financial backing to gamblers, offering to support William with a stake. However, he declines, wishing to avoid any liability that comes with such an arrangement.
As the story unfolds in Atlantic City, a convention attracts attention to the casino where Tell is present. He attends a seminar led by the retired Major John Gordo, acted by Willem Dafoe, but his discomfort leads him to exit rather quickly. On this exit, he is confronted by Cirk Baufort, played by Tye Sheridan, who gives Tell his contact information, revealing a connection that will significantly alter both their lives.
Cirk discloses shocking truths about Tell's past as PFC William Tillich, a soldier linked to the controversial Abu Ghraib prison scandal. This revelation ties into Cirk’s own family tragedy; his father, Roger Baufort, also suffered as a result of the prison’s dark legacy, battling addiction and ultimately taking his own life. Seeing Gordo as the figure responsible for their pain, Cirk seeks revenge and requests Tell’s assistance in his vengeful endeavor. While refusing to assist in a plan of violence, Tell instead offers to include Cirk in his gambling life, hoping to steer him away from a destructive path.
The plot thickens when Tell shares his aspirations with La Linda, expressing a desire to enter the World Series of Poker tour. His goal is to accumulate winnings that would enable Cirk to pay off debts and start anew. Along the way, Tell faces off against Mr. USA, a brash Ukrainian gambler, and builds a supportive relationship with both Cirk and La Linda, albeit cautious not to get too emotionally involved.
As tension builds, Cirk reveals his intentions to kill Gordo. Disturbed, Tell attempts to dissuade him by offering $150,000 from his own gambling earnings—an amount substantial enough for Cirk to address his obligations and return to his estranged mother in Oregon. Despite a heartfelt intervention, Cirk chooses a darker path, winding up at Gordo's house, and the news soon reveals a tragic confrontation that leaves both Tell and Cirk shattered.
In a gripping turn of events, Tell drives through the night to confront Gordo. He fully prepares for an intense showdown, showcasing the same behavior he employed in motels by covering the furniture. What follows is a harrowing encounter in which Tell, armed but conflicted, confronts Gordo not to kill him, but to undergo a "dramatic reenactment" of their haunting shared past. The sounds of their agony echo through the house before Tell emerges, gravely injured yet still alive.
Ultimately, Tell finds himself back in military prison, reconciling with the austere life he believes he deserves. In a poignant moment, La Linda visits him, and the two of them connect through the glass barrier separating them, each sharing an intimate touch as they grapple with the heavy burdens of their choices and the consequences that follow.
