A Town Called Mercy is the third episode of the seventh series of Doctor Who. It stars Matt Smith as The Eleventh Doctor, Karen Gillam as Amy Pond and Arthur Darvill as Rory Williams. It was written by Toby Whithouse, who has written three other episodes of Doctor Who.
The episode is set in the 19th Century Old West of the United States, and follows many of the tropes of the Western genre, although with Doctor Who's usual science-fiction elements. The Doctor, Amy and Rory find the titular town called Mercy, which is in crisis: the town is blockaded by a cyborg who is out to get a town resident, who turns out to be an alien refugee. The Doctor wants to protect this other alien (who is also a doctor). However, he finds out that the cyborg and the doctor are not the predator and victim they seem to be.
Doctor Who stories can go one of two ways. In some, the show's own convoluted history, ridiculous premise and discongruous situations are highlighted. Such was the last episode, Dinosaurs on a Spaceship. This episode, however, if stripped of all its science-fiction trappings, would still be a powerful story, with its thematic message of mercy, judgment, sacrifice and redemption. It naturally builds on the story arcs and character development that we have been seeing in Doctor Who, without calling attention to such things. And the acting, direction, cinematography all feed into this, with the episode being more focused on close shots and dialog than in other stories. This episode was more of a drama than an adventure, something that it is good to see in Doctor Who.
Based on the script and performance, I can't think of a better episode of Doctor Who in the past seven series (although other episodes have been better in using the more unusual aspects of the show's premise).
I have written this before reading any other reviews of the episode. It will be interesting to see if others liked the episode, and if they did, for the same reasons that I have mentioned here.