In 1843, former president Andrew Jackson asks Texas cattleman and long-time compatriot Devereaux Burke to help prevent the Republic of Texas from signing a treaty with Mexico and, instead, agree to annexation by the United States. Dev claims that he now has no interest in politics, but agrees to help Jackson, who fears that the treaty will undermine the Union, if he is awarded the contract to supply beef for troops needed in a possible war with Mexico. Jackson agrees and asks Dev to find Texas pioneer Sam Houston, who has recently spoken against annexation but is now living among the Indians. Jackson also warns Dev about opposition leader Thomas Craden, a wealthy Austin rancher. On his way to Austin, where he is to meet Jackson's loyal old friend, Minniver Bryan, Dev is attacked by Comanche and is only able to save himself with the aid of a passing rider. Dev, who does not mention his name, is startled when the stranger, whom he immediately likes, says that he is Tom Craden. The two arrive in Austin just as Luther Kilgore, a close friend of Dev and Jackson, is making an impassioned speech against the Mexican treaty. In order to defray the growing antagonism in the crowd, Dev shoots Luther in the arm. Tom, who is impressed by Dev's action, introduces him to Martha Ronda, a Texas patriot who runs the Austin newspaper and is loved by Tom. Dev is immediately attracted to Martha, but she seems uninterested and later warns Tom that she is suspicious of his new friend. Meanwhile, Dev finds Minnie, who tells him that twelve of his men are in town. Dev reveals his mission to the men, promising each $5,000 for joining the cause. Several offer to work for free, but Dev insists that he wants no "glory-getters." That night, Dev attends a formal dinner at Tom's hacienda. Martha acts as hostess to the Texas senators whom Tom is trying to persuade to switch sides and oppose annexation. After dinner, Tom tells the senators that Mexico has promised California to Texas and reveals his dream of having Texas become the largest republic in the world. Senator Claude Anthony Demmet is so incensed by Tom's revelation that he starts to leave, but Tom stops him, insisting that the senators will be his "guests" until after the treaty is signed. The senators ask for satisfaction from Tom, with Demmet the first to confront him with a dueling pistol. Although Tom could easily kill the senator after Demmet's shot only grazes him, Tom fires into the air. Martha is proud of Tom, but when she is alone with Dev realizes her attraction to him and they kiss. Not wanting to betray Tom's hospitality, Dev leaves and later relates what has happened to Minnie, who warns him that Martha will not return his feelings if she finds out what side he is on. That same night, after informing his men that he is going to look for Houston, Dev returns to Tom's hacienda and tells the senators to leave. Tom allows them to go, after which Dev reveals his true identity and confesses that he had earlier kissed Martha. Tom lets Dev leave, but Martha is so enraged to learn Dev's true identity that she urges Tom to go after him. Dev is able to elude Tom and his men by crossing the river into Apache territory, where he is lead to Houston's camp. When Dev tells Houston that the treaty with Mexico is soon to be passed, in part because Houston seemingly endorsed it, Houston assures Dev that he was merely trying to spur annexation supporters into action. Just then Tom finds his way into camp and accuses Houston of betraying the Republic. Houston then writes a letter for Dev to deliver to current Texas president Anson Jones, informing him of Houston's opposition to the treaty. Tom leaves before Dev, and gathers his men on the other side of the river to ambush him. Dev pretends to fall off his horse, then escapes downstream to surprise Tom's men. Although Dev has a clear shot at Tom, who has lost his gun, Dev does not kill him. Dev then rides to see Martha, and shows her the envelope containing Houston's letter. He tells her to tear it up if she wants, but she cannot, and the pair share a passionate kiss. The next morning, Martha reads an eastern newspaper story about the scandal surrounding Dev's contract for providing beef to the Union. Now convinced that Dev is an opportunist, she goes to President Jones. Dev arrives a moment later with the letter, but when he opens the envelope, discovers that the ink smeared when he fell into the river. Although Jones is willing to wait for Houston before bringing up the treaty in the legislature, Martha tells him about Dev's beef contract, and Jones decides not to delay. While Dev confers with Minnie and his men, Martha prints a story in her newspaper announcing Houston's endorsement of annexation, and later tells Jones and Dev that she has confirmed it is true. When Tom reads the article, he fears that the treaty will not be ratified and gathers supporters to storm Austin. Upon learning of Tom's plans, Dev becomes incensed and organizes the town to make a stand against him. As the legislature prepares to vote, Tom's men ride into town and a furious battle ensues. Tom's men break through the barricades and are ready to storm the legislature when Houston arrives with a large contingency of Indians. Tom loudly accuses Houston of selling out Texas, prompting Dev to fight him. During the fight, Tom returns Dev's earlier favor by sparing his life, but is finally bested by Dev. With annexation now a certainty, Houston warns that Mexican troops will attack and announces that the Americans are coming to their aid. Before joining the fight, Dev kisses Martha, and Tom joins his fellow Texans by carrying their flag into battle.
