The film opens in March 1836 in the Mexican state of Coahuila y Tejas, at the site of the Alamo in the town of San Antonio de Bexar, where the aftermath of a fierce battle leaves the bodies of both Texan defenders and Mexican assailants scattered across the ground. The narrative then takes us back a year prior, where Sam Houston attends a lively party aimed at rallying support for migration to Texas. At this gathering, he encounters David Crockett, who has recently lost his congressional seat. Houston informs Crockett that newcomers to Texas are entitled to claim 640 acres of land, prompting Crockett to wryly inquire if this new republic will require a president.
In San Felipe, Texas, members of the provisional government convene to deliberate over their recent victory at the Alamo and Bexar against Mexican forces in the initial Battle of San Antonio de Bexar. With Texas rebelling against the tyrannical rule of President Santa Anna, who commands an army to reclaim the Alamo, the Texas War Party pushes for military action to advance into Mexico and confront the enemy at Matamoros. Meanwhile, the Opposition Party advocates for strengthening the Texan army and establishing a recognized government. Ultimately, the provisional government votes to remove Houston from his position as commander. Disheartened, Houston expresses his disdain to Jim Bowie over drinks and urges him to obliterate the Alamo.
William Barret Travis (played by Jason Patric) arrives in San Felipe, eager to earn respect as a lieutenant colonel in the Texas Army. His storyline reveals his troubled personal life, including a divorce stemming from his own abandonment and misconduct. Soon, he receives orders to head the defense at the Alamo, where he meets Col. James Neill (Brandon Smith), who informs him that Travis will be in charge while Neill is on leave. Alarmed by the prospect of facing a vastly superior Mexican army, Travis frantically sends out for reinforcements as a few small groups of Texans trickle in.
Crockett makes his entrance in San Antonio with a defiant proclamation: “I told them folks you’all can go to hell, I’m going to Texas.” The mood shifts as the defenders express urgency for Santa Anna's inevitable arrival, leaving Crockett confused about the status of the fighting. Soon after, the feared Santa Anna (Emilio Echevarría) arrives in San Antonio, catching the Texan fighters by surprise. The Texans retreat into the Alamo compound, preparing as best as they can for the impending siege. Amidst the increasing tension, Travis writes desperate appeals for help, but only a handful of men respond.
As Santa Anna's forces establish a blockade around the Alamo, the siege commences. A pivotal moment occurs when Bowie seeks a diplomatic resolution with General Manuel Castrillón (Castulo Guerra), only to have Travis abruptly end negotiations by firing a cannon, effectively dooming their chances for peace. Travis offers a chance for those inside to leave, but nearly everyone chooses to stay and defend the Alamo. Among them is Mrs. Susanna Dickinson (Laura Clifton), whose husband is determined to fight.
As the siege intensifies, Bowie falls gravely ill, unable to participate in the defense, while night after night the Mexican army taunts the Texans with music and prepares for an all-out assault. As dawn breaks on March 6, 1836, Crockett, hardly having slept, signals the alarm at the sight of the approaching enemy. The battle cry of the Mexican forces echoes: "Viva Santa Anna!" Despite fierce resistance, the Mexican army breaches the Alamo walls. Tragically, Travis meets his end, shot in the head, while Bowie valiantly fights but is ultimately overwhelmed.
Crockett and the remaining defenders retreat to the chapel, where they make a last stand. As the Mexican troops capture the structure, Crockett offers a mock surrender, suggesting he could safely lead them to Sam Houston. In an act of vengeance, Santa Anna orders him executed, and Crockett falls heroically.
Days later, as news of the Alamo's fall spreads, Houston takes charge of a ragged Texan army and orders a retreat known in history as the "Runaway Scrape," narrowly evading Santa Anna's advancing forces. Against his advisors' counsel, Santa Anna splits his army, underestimating the Texan resolve. Eventually, the Texan forces gain their footing at San Jacinto, surprising their adversaries during their mid-day rest.
On April 21, 1836, armed with cannons and support from Tejanos, Houston orchestrates a decisive assault during the Battle of San Jacinto, achieving significant success and capturing Santa Anna, who is forced to concede to Texan independence. The final moments of the film capture the haunting spirit of Crockett, playing his fiddle atop the Alamo, gazing out into the horizon, symbolizing the enduring legacy of those who fought.
