This week’s story starts with a voiceover — a little unusual, but it happens occasionally. A woman tells us that her favorite story was about a man who lived forever and fell from the stars, whose eyes were heavy from the weight of all they’d seen. We cut rather quickly to a pursuit in the desert. A man who has a metal light for an eye, who looks a lot like Community’s Kickpuncher, has cornered his prey and demands the man make peace with his gods. “Once they were your gods, too,” the man responds. He lunges for a weapon, but Kickpuncher shoot him before he can reach it. As he dies, the man questions if he’s the last one left. Kickpuncher solemnly answers there’s one more — the Doctor. CUE THEME SONG
We join the Doctor, Amy, and Rory at the entrance to the town of Mercy in America. There’s a Keep Out sign and an odd barrier of stones and wood making a line around the town. Naturally, he decides to enter anyway, since he doesn’t take orders from anyone. As they walk through the town, he points out the electric street lamp is 10 years too early, which when combined with the Keep Out signs and the people staring angrily at them, means something is off in the town.
The moment they enter the lively saloon, the music halts and everyone stares. The Doctor finds this the perfect time to test out his American accent and introduces himself as the Doctor. The entire room stands and a man, the undertaker, begins to measure the Doctor. A young man, ?, asks if he’s an alien, which he naturally answers yes. The entire saloon carries the Doctor off, dragging the protesting Amy and Rory behind them. They literally toss the Doctor out of the town, keeping him from crossing back over the stone and wood line at gunpoint.
The preacher begins to pray as Kickpuncher appears behind the Doctor. A man named Isaac fires his gun in the air and tells the Doctor to cross the line. As soon as he does, Kickpuncher disappears. The young man argues that our Doctor could be The Doctor, the one that this Kickpuncher figure wants, but Isaac seems certain he isn’t.
The Doctor, Amy, and Rory follow Isaac into the prison where he explains that this Kickpuncher, who is in actuality called the Gunslinger, is keeping the town prisoner. The line around the town appeared one morning and nothing can come past it or the Gunslinger will shoot. Isaac shows them a Stetson that was shot, which naturally horrifies the Doctor, who’s had a number of his own hats shot. The Gunslinger’s one demand is that they hand over the alien Doctor.
Rory wonders how the Gunslinger could know they were there, since they were supposed to be going to the Day of the Dead festival in Mexico. The Doctor accuses them of spilling crumbs on the console, before demanding to see the Doctor that’s already there. He reasons that Isaac’s confidence in him not being the desired Doctor means Isaac already knows who it is.
A man with an interesting face tattoo stands up behind the prison bars and introduces himself as the alien Doctor, Kahler-Jex. The Doctor is impressed, as the Kahler race is one that could build a spaceship out of nothing more than Tupperware and moss. Jex says his spacecraft crashed a mile outside of town and was too broken to repair, so he stayed on as a Doctor to repay his debt to them for helping him out. In his time there, he stopped cholera from taking a single life in the town, and used his ship as a generator for heat and light in the town.
The Doctor wonders why the Gunslinger wants him, but Isaac insists it doesn’t matter, because the town won’t hand him over. They make a plan for the Doctor to retrieve his TARDIS and evacuate the town. First the Doctor needs a way to get to the TARDIS quickly. He asks the preacher to borrow his horse Joshua, but the Doctor speaks horse, and the horse says his name is Susan and he wants the preacher to respect his life choices.
As Rory and Isaac run through the desert pursued by the Gunslinger, Amy and Kahler-Jex wait. They talk about how he feels like he can start afresh here and help people, which is all he’s ever wanted to do. He says he can tell she’s a mother, and she asks if he’s a father. He says yes, in a way. Who wants to bet he created the Gunslinger?
Meanwhile, the Doctor and Susan find a wire in the desert. It leads to a big white egg-like thing covered by a sheet, which must be Kahler-Jex’s ship. Susan points out that it appears to be undamaged, so the Doctor begins jumping up and down, hitting it with his hand, trying anything to get it to open. He uses his sonic screwdriver, and a blaringly loud alarm goes off. The Gunslinger, who’s cornered Rory and Isaac, recognizes it as a Kahler Alarm, and goes off to investigate. Back in the town, Kahler-Jex and Amy hear it as well, realizing the Doctor isn’t following the plan.
The Doctor naturally enters the ship and uses his sonic screwdriver to override the password. He wants information on the Gunslinger, but since the computer doesn’t have any, he settles for information on Kahler-Jex. The computer tells him that names of deceased subjects can be found on the dropdown menu. All we can see is the Doctor’s face as the info flashes by and voices on some sort of video scream. Clearly, the science this other Doctor was involved in was not pleasant.
Gunslinger is waiting for him when he exits. The Doctor tries to reason with the Gunslinger, that they could find another form of justice that would satisfy the Gunslinger, but he disagrees and says there wil be no more warning shots — the next person to step over the line will be killed.
Meanwhile, Kahler-Jex has pulled a gun on Amy. Isaac and the townspeople are unaware of his past, but now that the Doctor’s gone off the plan, they’re sure to find out and be unhappy with him. He plans to take Amy with him, since the Gunslinger won’t shoot if innocents coud be hurt, but before he can leave, Isaac and Rory return.
The Doctor arrives and tells them what he’s learned. Gunslinger is a cyborg, half man half machine, that Kahler-Jex built. After a nine year war had destroyed half their planet, he and a group of scientists took volunteers for “special training”and experimented on them to create killing machines. They saved millions of lives, but the Doctor points of that they also killed many during the experiments.When the war ended, Gunslinger’s circuity had faulted somehow, and he began hunting down the team who created him. When there were only two left, they escaped the planet and ended up crashing here in Mercy, but now Kahler-Jex was the last one left.
Rory thinks they should kick Kahler-Jex out of town, but Amy disagrees vehemently, because they don’t just let people get executed. Kahler-Jex accuses the Doctor of not having the nerve to do what needs to be done. The Doctor shoves Kahler-Jex out the door in anger, pushing him through the town and across the line to have him killed, going so far as to draw a gun on him. Amy shoots a gun into the air and demands the Doctor let him back in or she’ll shoot him. When he says she’d never do that, she bites back that maybe she’s changed, hinting that it’s really him that’s changed. Finally, the Doctor admits that he’s willing to kill Kahler-Jex to save everyone in order to make up for all the people that he’s lost, whose deaths he caused, because of his mercy. Amy smiles sadly at him, saying this is what happens when he’s alone, and reminds him that they’re supposed to be better than that. It’s easily one of the most powerful scenes in the episode, and one of the strongest between Amy and the Doctor on the show as a whole.
But it’s too late — Gunslinger has arrived and is preparing to shoot. At the last second, Isaac pushes Kahler-Jex out of the way and gets hit instead. As he dies, he asks the Doctor to protect Jex and the town for him and gives him his Marshall’s badge. The Gunslinger gives them an ultimatum: hand over Jex by noon tomorrow, or they all die.
That night, the town questions the Doctor’s sudden change of heart. The same young man from earlier believes its Kahler-Jex’s fault Isaac is dead, and only his death will protect the town. He tries to goad the Doctor into a gunfight, but the Doctor recognizes that he’s young, reckless, and doesn’t really understand the consequences. He convinces him to stand down and give the Doctor a chance to save the town his way.
Inside, Kahler-Jex tries to convince the Doctor to let him surrender. His people believe that when you die, your spirit has to carry the souls of all the people you’ve wronged up a mountain. He knows the weight he’ll have to lift is huge, and grows every day the Gunslinger kills more people instead of him. The Doctor seems to sympathize with that.
It’s five minutes until noon the next day. The Doctor waits in the center of town. The preacher and the townspeople are hiding in the church, praying. The Gunslinger appears at the border of town and crosses the line the second the clock strikes noon. He and the Doctor face each other, hands over their guns, and then draw — but the Doctor draws his sonic screwdriver instead and explodes all the windows and lights, throwing the Gunslinger off and running away.
Amy lets Kahler-Jex out. Rory and a few of the other men in the town have painted Kahler-Jex’s tattoo on their face are are racing through the town as a distraction, so Kahler-Jex can get out of town. Gunslinger scans their faces and recognizes that it’s the wrong facial match. He walks through the town past the church, where a little girl accidently knocks over a few books. Thinking Kahler-Jex might be inside, he bursts in. He thinks about shooting them, like he threatened, but he sees the little girl and how afraid they all are, and simply leaves.
He finds the Doctor and threatens him, but Kahler-Jex’s voice echoes through the town. He’s reached his ship and asks is the Gunslinger will go home when this is over. Gunslinger says he couldn’t because he’s a monster now, but that he’ll tear the universe apart in order to kill him. Jex recognizes this and set the ship to self-destruct. He doesn’t want to risk another innocent planet or race and is ready to face the souls he’s wronged. His ship blows up before they can do anything.
The Doctor offers to take the Gunslinger home, but he says now that it’s over, he’ll just go self-destruct in the desert because he’s a creature of war and has no part to play in peace time. The Doctor suggests he could protect it instead.
As the Doctor leaves to drop Amy and Rory off at home once again, the voiceover returns. The woman tells us that America is a land of second chances, which the Gunslinger has clearly accepted. We learn she’s been told this story by her great-grandmother, who must’ve been the little girl that knocked the books down in the church. Apparently, the town of Mercy no longer has a sheriff or a marshal, because the Gunslinger is their own special angel watching over them.