Plot

A spaceship arrives in 1873 Arizona to take over the Earth, starting with the Wild West region. All that stands in their way: a posse of cowboys and natives.

The Old West.. where a lone cowboy leads an uprising against a terror from beyond our world. In 1873 in the New Mexico Territory, a stranger with no memory of his past stumbles into the hard desert town of Absolution. The only hint to his history is a mysterious shackle that encircles one wrist. What he discovers is that the people of Absolution don't welcome strangers, and nobody makes a move on its streets unless ordered to do so by the iron-fisted Colonel Dolarhyde (Ford). The town of Absolution lives in fear. But Absolution is about to experience fear it can scarcely comprehend as the desolate city is attacked by marauders from the sky. Screaming down with breathtaking velocity and blinding lights to abduct the helpless one by one, these monsters challenge everything the residents have ever known. Now, the stranger they rejected is their only hope for salvation. As this gunslinger slowly starts to remember who he is and where he's been, he realizes he holds a secret that could give the town a fighting chance against the alien force. With the help of the elusive traveler Ella (Olivia Wilde), he pulls together a posse comprised of former opponents-townsfolk, Dolarhyde and his boys, outlaws and Apache warriors-all in danger of annihilation. United against a common enemy, they will prepare for an epic showdown for survival.—Universal Pictures

In the Old West, an amnesiac stranger awakes in the middle of the desert wounded in the belly with a bracelet in one of his wrists. He is attacked by thieves but defeats them. He rides a horse and heads to a former mining town, where the local preacher treats him. Then he sees the youth Percy Dolarhyde, who is the son of the powerful farmer Woodrow Dolarhyde, bullying with the bar owner Doc and the other locals. When Percy provokes the stranger, he reacts and beats up on Percy. The local Sheriff John Taggart arrests Percy and he finds that the stranger is the wanted Jake Lonergan. The sheriff returns to the bar with his deputies to arrest Jake, but he subdues the men. However he is hit on his back by the mysterious Ella Swenson and faints. Jake is arrested and when Sheriff Taggart is ready to take Jake and Percy in a coach to deliver to a Federal Marshall, Woodrow arrives with his men ready to protect his son. But they are attacked by spacecrafts that abducts several dwellers, including Percy, Doc's wife, and the Sheriff. Woodrow organizes a posse to seek out the kidnapped people in a dangerous journey against an advanced race of aliens. Meanwhile Jake Lonergan has glimpses of his past life and they learn that someone among them may help them in the fight.—Claudio Carvalho, Rio de Janeiro, Brazil

In 1873, Arizona Territory, an unnamed loner (Daniel Craig) wakes up in the desert injured, with no memory and with a strange metal shackle on his wrist. The loner is not able to get off the shackle even after hitting it with rocks. After killing three drifters who try to rob him, he takes their clothes, weapons and a horse. He wanders into the small town of Absolution and walks into an empty church building to find food and shelter. The local preacher, Meacham (Clancy Brown) finds the stranger. The stranger was shot in the abdomen and was bleeding from it. The wound was odd looking and was almost cauterized already. After initial distrust, Meacham decides to treat the stranger's wound. Meacham says that Absolution was a mining town, but people moved on after they did not find any gold.

Doc (Sam Rockwell) is the town's doctor and owner of Absolution's saloon. Maria (Ana De La Reguera) is the saloon maid and the Doc's wife. The stranger subdues Percy Dolarhyde (Paul Dano), a volatile drunk who has been terrorizing the town. Percy was threatening Doc for charging him for his drinks and says that it is only because of his dad, the cattle rancher, that there is any business in town. Percy then proceeds to collect tax from all the town folks and shoots a deputy, while threatening the stranger when he refused to pay. The Sherrif arrests Percy. Nat Colorado (Adam Beach) is Dolarhyde's Native American right-hand man and he leaves to inform Dolarhyde about Percy's arrest.

Sheriff Taggart (Keith Carradine) recognizes the stranger as Jake Lonergan, a wanted outlaw, and attempts to arrest him. Jake beats up the posse sent to take him in and nearly escapes, but a mysterious woman named Ella Swenson (Olivia Wilde) knocks him out. Taggart and his men prepare to transport both Jake and petulant young drunkard Percy Dolarhyde to Santa Fe for trial.

Percy's father, Colonel Woodrow Dolarhyde (Harrison Ford), a wealthy and ruthless cattleman, arrives with his men and demands that Percy be released. He sees Jake and also demands he be released to him, since Jake was the one who stole Dolarhyde's gold. During the standoff, an alien craft begins attacking the town. The alien craft is using laser-based energy weapons. Percy, the sheriff and many other townsfolk are grabbed by long, whip-like feelers hanging from the bottom of the alien ships and are abducted. Jake's shackle unfolds and becomes a weapon, shooting down one of the ships with a single shot, ending the attack.

Dolarhyde, Ella, and other townsfolk form a posse to track an injured alien that escaped from the downed ship. Jake, meanwhile, travels to an abandoned cabin, and in a flashback, recalls returning there with the gold just before he and a woman, Alice (Abigail Spencer), were abducted by the aliens. His memories returning, Jake joins up with the posse. During the night, while they camp in an upside-down paddle-wheel steamboat that the aliens apparently dumped far from any large river. The alien they were tracking kills Meacham, who sacrifices himself to save Emmett (Noah Ringer), Taggart's grandson.

By the next morning, most of the posse has deserted, and the others are attacked by Jake's former gang. Jake, who stole the gang's loot after their last heist, attempts to retake control, but fails. As he and the others flee, the aliens begin attacking again and Ella is captured. Jake jumps aboard the ship and attacks the alien pilot, causing the ship to crash, but Ella is fatally wounded. Jake kills it with his wrist-blaster.

Quite shortly after the crash, however, the posse is captured by Chiricahua Apache Indians, who blame them for the alien attacks. As Ella's body is dumped on a fire by a Chiricahua warrior, she is fully resurrected. Ella reveals herself to be from another alien race, who had traveled to Earth to help resist the invaders after they destroyed her home world.

The aliens, who have been abducting humans to perform experiments, are also mining gold to power their machines. They are not invulnerable, however: Jake's gauntlet weapon can kill them, as well as stabbing and shooting them, though the creatures are far stronger and more durable than humans and have superior weapons. Only Jake's wrist weapon or a well-aimed round from a rifle can kill them with a single shot. Ella tells them that the previous attackers were just scouts.

Ella claims Jake holds the secret to the aliens' whereabouts and says they must stop them before they exterminate all life on the planet. After taking medicine offered by the Apaches, Jake recalls that Alice was Euthanized after she was used in an alien experiment, but he escaped, inadvertently stealing the alien weapon in the form of a gauntlet. He could also remember the location of the aliens' base of operations.

Armed with this knowledge, the group, now led by Dolarhyde, prepares to attack the aliens' grounded mothership. Jake returns to his old gang and persuades them to join the fight. In a sneak attack, the humans breach the spaceship by destroying the shuttle bay, forcing the aliens into a ground battle. Jake and Ella board the ship and free the captives, but Jake is captured. Dolarhyde rescues him and both men escape the ship after killing the alien responsible for Alice's death, identified as Jake left a distinctive scar on its eye in his original escape.

The ship takes off as the remaining aliens flee Earth, but Ella stays on board to end the threat: she sacrifices herself by entering the ship's core and turning Jake's wrist weapon into a bomb; it detonates, obliterating the ship.

Jake's memory partially returns, and some abducted townsfolk begin to remember their past. Still a wanted man, Jake decides to leave; the sheriff and Dolarhyde say they will claim that he was killed in the invasion. The citizens intend to rebuild the town with the expectation that the newly discovered gold mine will soon bring many new settlers. Jake kindly rejects Dolarhyde's offer to help rebuild the town, and rides away.