Lieutenant General Eugene Irwin (Robert Redford) finds himself in a maximum-security military prison, serving a ten-year sentence for disobeying a presidential order that led to the tragic deaths of eight soldiers during a mission in Burundi. The prison's commandant, Colonel Winter (James Gandolfini), initially admires Irwin but quickly becomes offended by a remark he overhears. Irwin criticizes Winter's collection of military artifacts, particularly a set of used Civil War bullets, suggesting that no true combat veteran would ever hold such items in esteem. This comment stings Winter, who has never experienced combat, leading to a rapid decline in his respect for Irwin.
In an effort to maintain some justice within the prison's harsh environment, Irwin intervenes when a guard attempts to punish a prisoner, Corporal Ramon Aguilar, who made the mistake of saluting him in the yard. As Irwin witnesses the ongoing brutality within the facility, he hopes to foster unity among the inmates by constructing a "castle wall" using stone and mortar that symbolizes their resilience. However, Winter, envious of the respect Irwin commands, orders the wall's destruction. In a heart-wrenching moment, Aguilar bravely stands in front of a bulldozer, only to be struck down by a rubber bullet fired at close range by a sharpshooter under Winter's command.
After the devastation of the wall, Irwin and the prisoners honor Aguilar, who bravely attempted to assert their dignity, by paying their respects in formation. When Winter tries to reconcile with Irwin, he is met with scorn and called a disgrace, prompting the general's refusal to entertain any further conversation. The atmosphere shifts as the prisoners adopt military-like behavior around Irwin, which infuriates the commandant. Seeking an edge, Winter enlists the help of Yates (Mark Ruffalo), an anti-social inmate with a background as an Apache pilot, offering a reduced sentence in exchange for information on Irwin's plans.
Irwin deftly plots to incite chaos within the prison to reveal Winter's inadequacies as a leader to Brigadier General Wheeler (Delroy Lindo), who is set to visit. In anticipation of Wheeler's arrival, Winter receives a threatening letter about a supposed kidnapping scheme orchestrated by the inmates. However, when the situation escalates, he uncovers that it was a ruse designed by Irwin to test the guards’ responses in the event of a real uprising.
As the riot unfolds, the prisoners arm themselves with improvised weapons resembling those from medieval times, successfully commandeering an armored vehicle and a prison helicopter. They reach out to Wheeler, informing him of the siege, but Winter, racing against time and his own failing command, resorts to threatening the prisoners with live ammunition. Irwin, aware of the severity of the moment, commands his men to raise the American flag upside down—a distress signal that underscores their plight.
In a clash of wills, Winter tries to order his men to open fire on Irwin, yet they rebel against his command, demonstrating their loyalty to the general. In a shocking twist, Winter, unable to enforce his authority, takes matters into his own hands and fatally shoots Irwin. However, as Winter faces being arrested by his own second-in-command, Captain Peretz, the flag is ultimately raised correctly, symbolizing not just their struggle but their respect for camaraderie and sacrifice.
As Brigadier General Wheeler arrives at the prison, accompanied by the distressing sight of Winter being led away in handcuffs, the story concludes with the inmates embarking on a new mission: to build a memorial wall, honoring both Aguilar's and Irwin's bravery, forever etched into the stone—reminders of their shared humanity within the confines of a cruel prison system.
