When the Doctor tries to step back over the line, about a dozen men draw their weapons. "He's comin'," says the preacher. In the distance, the chapeau-wearing drone teleports towards the town in increments of a few yards each. Seems like it would almost be easier to just walk over. The Doctor looks behind him to see what's got the townsfolk so spooked and gets an eyeful of the drone. Someone shoots into the air. It's Ben Browder wearing a marshal's badge and an unfortunate mustache. "You! Bow Tie! Get back across that line." Relieved, the Doctor does as he's told. The drone vanishes. The young man from earlier turns to Marshal Ben. "Isaac, he said he was a doctor -- an alien doctor." Isaac reminds the young man that he knows darned well this isn't the right doctor.
Isaac brings the visitors to the town's jail. "What was that outside?" the Doctor asks. "It was the Gunslinger," says Isaac. He showed up three weeks ago and laid down the borderline. Nobody's been able to go in or out of town since. Isaac tosses him a hat with a bullet hole in the crown to show what happened to the last person who tried to leave town. Luckily it was just a warning shot, although the Doctor is a bit aghast that a hat has been injured so cruelly. "He says he wants us to give him the alien doctor," Isaac says. "But that's you," Amy says. "Why would he want to kill you? Unless he's met you." Heh. Rory points out that nobody should even know they would be there, since they were actually aiming for Mexico. They're like Bugs Bunny. Always taking that wrong turn at Albuquerque and ending up God-knows-where. The Doctor has surmised that there's another alien doctor in town and he wants to meet him. He's also figured out that this mystery doctor is the one who set up the town's electricity and that Isaac's got him hidden somewhere in the jail.
And indeed, he's in one of the cells. He throws off his concealing blankets and reveals himself to be a prim little gentleman in bowler hat and pince-nez glasses. He has a tattoo like the man at the beginning of the episode. "My name is Kahler-Jex," he says. "I'm the doctor." Ah, this show. Expanding my Word dictionary one weird character name at a time. The Doctor turns into a big fanboy because the Kahler are just such a super neato race. "They could build a spaceship out of Tupperware and moss!" gushes the Doctor, shaking Jex's hand for too long. Amy has to pry the Doctor away before he can reveal the Kahler fanvids he's made using all his favorite Katy Perry songs. When Jex's ship crashed in the desert, Isaac and the other townsfolk saved him, so he stayed on as their doctor. "On my world, I was a surgeon, so it seemed logical," he explains. Since then, he's cured a cholera outbreak and used his ship to generate electricity for the town.