The Doctor, Amy and Rory are on their way to Mexico for some Day of the Dead fun when they instead find themselves in the Old West. They decide to have a look around the nearest town, the bustling metropolis of Mercy with its population of 81 people. They immediately notice that surrounding the town is a borderline of sticks and stones. They also notice that the town has electricity a few years before it should. The Doctor gets a welcome that's a little less than warm when he cheerfully confirms that he's not just a doctor, but an alien, to boot. The people of Mercy push him right back out of town and past the borderline.
A cyborg gunslinger has set up the border with the promise that anyone who steps beyond it will be killed. He's in search of an alien doctor, but not our alien Doctor, as Isaac, the town's sensible marshal, reminds his frightened citizens. No, that doctor is a man named Kahler-Jex, and the town has been harboring him since his ship crashed outside of town some years ago. He cured a cholera outbreak and brought electricity to the town, but a lot of people are starting to consider handing him over to the cyborg. At first the Doctor's like, "Oh, no we can't do that!" But then he finds out that it was Jex himself who created the cyborgs as part of his home world's war effort. He's trying to make amends now, but an enraged Doctor drags Jex to the edge of town, ready to hand him over to the cyborg. Amy has to remind him that, hey, this isn't what they do. Unfortunately, there's a skirmish and Isaac ends up dying. With his last breath, he asks the Doctor to save Jex.
Jex has other ideas. While half the town is running around trying to save him, he flees to his crashed ship. He activates its self-destruct mode and kills himself in a fiery explosion. Meanwhile, the Doctor has been getting to know the cyborg a bit. He's not really a bad guy, but he was made for a war that's over. He plans to finish himself off, but the Doctor suggests he may have a new purpose now. The episode ends with the cyborg watching over the little town and protecting it from afar. Stay tuned for the full weecap.
It was a dark and starry night. A woman's voice narrates: "My favorite story was about a man who lived forever, but whose eyes were heavy with the weight of all he'd seen... a man who fell from the stars." It sounds like she's talking about the Doctor, but you know how this show likes to have characters describe things that sound really obvious and then it turns out later they were talking about something entirely. A small spacecraft descends toward the ground. It is being pursued by someone or something with a video screen that identifies itself as a Kahler Security Drone. "Terminate" flashes up on the screen. The ship is blasted and crashes in a heap. A man falls out. He has a raised tattoo on his face that the drone IDs. "I knew you'd find me eventually," the tattooed man says. "Make peace with your gods," the drone says in a deep, computer-distorted voice. The tattooed man reaches for a gun. The drone is wearing a cowboy hat and leather duster. He looks like Kryten from "Gunmen of the Apocalypse," but with Borg bits on his face and a huge gun where one of his arms should be. He shoots the tattooed man, who asks, "Am I the last one?" "There's one more -- the Doctor," says the drone. He shoots again, the flare from his gun taking us into the opening credits.
Daytime in the desert. Twangy music lets us know we're in America. The Doctor is standing in the middle of a dusty road on the outskirts of town called Mercy. He takes note of the sign that proclaims its 81 residents. Amy and Rory point out the line of rocks and wood surrounding the town. The Doctor sonics it to confirm that it is, indeed, made of rocks and wood. The Doctor and friends ignore the "Keep Out" sign and venture past the line into town. The drone watches from afar.
As they wander through town, they're greeted by the wary gazes of its citizens. The Doctor notices an electric streetlamp and says it's about 10 years early. The Doctor, of course, is tickled: "Anachronistic electricity, "Keep Out" signs, aggressive stares... has someone been peeking at my Christmas list?" They make their way into a saloon. Everyone stops what they're doing to gawk at the newcomers. Undeterred, the Doctor flirts a bit with the waitress and orders a cuppa tea. This just makes everyone gawk even harder. The town preacher stands up and asks, "Sir, might I inquire who you is?" "I'm the Doctor!" says the Doctor. Too bad he's not a grammar teacher. Before he can introduce Amy and Rory, the saloon patrons leap to their feet. The town undertaker starts measuring the Doctor for a coffin. A young man asks the Doctor if he's an alien. The Doctor happily admits that is. Suddenly, a group of men hoist him up and carry him to the edge of town. They toss him over the borderline of sticks and stones.