U.S. Marshal Howard Nightingale leads a well-trained posse of six men: John Wesley, John Lake, Krag, McCanless, Rains, and Reyno. He is also running for U.S. Senate. By bribing Pensteman, a member of Jack Strawhorn’s train robbery gang, to betray his companions, Nightingale and his men surround a barn where the outlaws are sleeping, set it afire, and kill every outlaw except Strawhorn, who shoots John Lake and steals his horse. Escaping to Tesota, Texas, Strawhorn kills Penstemen, and also murders the town sheriff, Buwalda, when the lawman attempts to arrest him. After Strawhorn leaves town, Nightingale’s personal train arrives, equipped with a passenger car and a large boxcar that contains a horse stables, boxes of dynamite, a printing press for making political and wanted posters, and a dark room for Nightingale’s personal photographer, Wiley. A ramp on the boxcar drops to the ground, allowing Nightingale and his men to ride their horses off the train, and the townspeople greet them as heroes. Meanwhile, in the nearby hills, Strawhorn joins Pepe, an outlaw he paid to assemble a new gang. He sets up an ambush for Nightingale at a mining camp, but when the posse arrives, Strawhorn’s gunmen fire too soon, and the professional man-hunters kill everyone except Strawhorn, who is captured and paraded back to Tesota. Wiley takes a photograph of Nightingale with his handcuffed quarry in front of the courthouse, then Strawhorn is locked in the county jail. He tells the marshal he no longer has the $40,000 his gang stole from the Texas and Arizona Railroad because the posse’s fire at the barn destroyed it. That night, during the town’s celebration of Strawhorn’s capture, Nightingale makes a lengthy political speech about the importance of law and order. The only Tesota resident unimpressed with him is Hellman, a one-armed, one-legged newspaper editor who thinks the marshal is too ambitious and too beholden to the Texas and Arizona Railroad, which supplies his personal train. During Nightingale’s lengthy speech, John Wesley makes love to Mrs. Katharine Cooper, the unfaithful wife of the local café owner, and deputies McCanless and Rains lure two young women into the train’s sleeping quarters. The various merchants watch with pity as Mr. Cooper abides the disappearance of his wife, and two of them, fathers of the girls, seethe with an anger they are too afraid to express. That night, Nightingale occupies the “presidential suite” of Tesota’s best hotel, run by Mrs. Ross. Though Mrs. Ross tries to seduce Nightingale, he fends off her attentions. Meanwhile, the disgruntled Wesley warns the other deputies that as soon as Nightingale becomes senator, he will abandon them. The next morning, aware of the disgruntlement, the marshal assures his men they will be hired by the railroad, but their jobs will pay less than their current wages. Nightingale locks Strawhorn in a cell built in his boxcar stable, and the train leaves for Austin, the Texas capital. Setting straw on fire to distract John Wesley, Strawhorn grabs his keys, and escapes by leaping on horseback from the moving train. Moments later, Nightingale stops the train and leads his posse after him, but Strawhorn doubles back and climbs into the locomotive. As Nightingale leaps into the cab after him, Strawhorn takes the marshal prisoner and handcuffs him. He puts the train in reverse and returns to Tesota, as the fire he set to escape spreads to the entire boxcar and touches off the posse’s dynamite. In Tesota, as the town’s firefighters put out the flames, Strawhorn carries Nightingale over his shoulder to the hotel and orders the presidential suite. When the posse arrives, Strawhorn instructs John Wesley to come to the hotel room, unarmed. Aiming a pistol at Nightingale’s head, he gives the posse ten minutes to replace the $40,000 it destroyed in the barn fire. Wesley and the others rob Tesota’s merchants, beat the ones who resist, and raise $30,000, which Strawhorn accepts as “close enough.” He returns the money to Wesley and tells him to distribute it evenly among the other posse members. When Mr. Cooper, the cuckolded café owner, goes after them with a gun, they shoot him dead. Strawhorn climbs on Nightingale’s horse and asks the posse members to join him. All but Krag accept the offer and ride out of town, leaving Hellman the key to unlock Nightingale’s handcuffs. The marshal and Krag stand alone, as the townspeople turn their backs and disappear into their homes.