Doctor Who-A Town Called Mercy

                          The doctor,Amy and Rory arrive in a 19th century American frontier town called Mercy,which has a puzzling keep out sign. When the doctor dismissively crosses that line,he finds a group of towns people drawing pistols at him. He and the Ponds are taken in by Sheriff Isaac,who at first tells them that a mysterious gunslinger is blocking the town off from food and supplies and killing anyone attempting to leave-that is until an "alien doctor" shows up whom he's looking for. When the doctor agrees to sacrifice himself to save the town,Isaac confesses the alien doctor is already in town. He is a Kahler Jex,a surgeon from a race of ingenious engineers who has not only cured a cholera epidemic in Mercy but also provided them with electric lighting. So the doctor agrees to go with Isaac,Amy and Rory to the outskirts of town to seek out the gunslinger pursuing Jex.

                   While he companions successfully fend off the cyborg gunslinger,the doctor manages to use his sonic screwdriver to to access the personal database in Jex's egg like spacecraft. He returns to the town to find the Jex has been lying all along. Jex was in fact a military surgeon who had created the gunslinger,actually called Kahler Tech,through cruel medical experiments on sentient beings. Tech has been pursuing him to gain justice for Jex's misdeeds as a war criminal. While the doctor is equally as furious,Amy reminds him of the irony of his attitude towards Jex-even as Isaac is killed in crossfire. Now the sheriff,the doctor agrees to protect Jex from his creation-even fending off the frightened towns people in a lynch mob. The situation is handled when the doctor agrees to face of Kahler Tech in a shoot out-creating a distraction while Jex escapes. Jex invariably agrees to end his life to face his misdeeds. Unsure of his place on his own world following Jex's death,Tech elects to remain as a peaceful protector of Mercy as the doctor and his companions depart in the TARDIS.

                  This is one of the strongest and most cleverly conceived stories of Matt Smith's time on Doctor Who. The plot itself blends the themes of revenge and redemption found in a quality  Western with a science fiction twist-in this case an alien character who attempts to redeem himself in a small and less advanced community to make up for his Nazi doctor-like war crimes. In a theme that's played out ever since Galifrey was destroyed in the last great time war,Jex and Amy alike both question the doctors anger at the immorality of Jex's actions and self preserving attempt at redemption. The doctor redeems this when he faces off the towns lynch mob,contradicting their original principles as they demand Jex be handed over to them,by delivering an iconic line: "Violence doesn't end violence-it extends it". Reminding himself of the oath he took for himself before his home world was destroyed,the doctor manages to restore the peace Mercy had found by part of the very means that almost threatened it in this quality story.