DOCTOR WHO IN DETAIL

In an American desert the Gunslinger is tracking down his latest victim, a scientist. Before the Gunslinger fires the fatal shot the scientist asks if he is the last one. The Gunslinger says there is one more - the Doctor.

Watched from the distance by the Gunslinger the Doctor, Amy and Rory are visiting the wild west town of Mercy, with a mere 81 residents. Around the town is a border of rocks and stones. The streets appear empty, and residents are watching from street corners and houses. A street lamp - an electric street lamp around ten years too early, starts to spark.

Moving further into town then make their way into a saloon bar. There are plenty of people in the bar, but they fall silent when the Doctor, Amy and Rory enter. One of the residents asks who the Doctor is, whilst an undertaker starts measuring him. When someone asks the Doctor is he is an alien he answers yes, and is immediately set upon by the people in the bar and carried out into the street and thrown out of the Mercy.

When the Doctor turns round everyone is pointing a gun at him. In the distance the Gunslinger appears. The Gunslinger disappears for a moment then re-appears closer. Then townsfolk are still pointing their guns at the Doctor to stop him re-entering the town. The local Marshall appears and tells the Doctor to get back over the line into Mercy. Once he does the Gunslinger disappears.

The Marshall explains that the Gunslinger appeared about three weeks earlier, and so did the border round Mercy. Nothing gets in, and nothing get out. People, and supplies, included. The Gunslinger has one demand: the alien doctor. The Doctor knows he is not the alien doctor the Gunslinger wants, and he knows that the Marshall - Isaac - knows where the real alien Doctor is.

In one of the cells a man reveals himself as Kahler-Jex - the alien doctor who is responsible for rigging up the electric lights in the town. The Doctor has heard of the Kahler - a resourceful species with a odd vein in their faces. Jex tells the Doctor that his craft crashed about a mile out town and he was rescued by Isaac. As he was a surgeon Jex stayed in the town as their doctor - including treating a case of cholera.

Jex's craft is badly damaged. The Doctor says he can fetch the TARDIS; there is enough room to evacuate the town. But that means getting past the Gunslinger. Isaac and Rory, with Rory wearing Jex's clothes, distract the Gunslinger whilst the Doctor borrows a horse - Joshua (or Susan as it prefers to be called) and rides back towards the TARDIS.

On the way the Doctor stops and examines the power line that had been set up by Jex. The Doctor follows it back to Jex's craft, which does not appear to have any damage. The Doctor uses the sonic screwdriver and opens the ship - but not before setting off the alarm which alerts the Gunslinger, and also Jex.

Inside the ship the Doctor is given ten seconds to enter the code before the ship self destructs. The Doctor overrides the security and asks the ship's computer about the Gunslinger, but the file is not found. Instead the Doctor asks about Kahler-Jex. and sees many distressing images.

Inside the Marshall’s office Jex has heard the alarm and raises a gun to Amy. There are things in Jex's past that he doesn't want Isaac to uncover, and plans to leave, taking Amy as hostage so the Gunslinger will not fire - he is programmed not to take innocent lives. Before Jex can leave Isaac stops him.

When the Doctor emerges from the ship he sees the Gunslinger. He asks the Gunslinger why he hasn't just walked into town and taken Jex, but the Gunslinger says people will get in the way. But the Gunslinger has waited too long, and says he will kill the next person who crosses the line - and to make sure it is Jex.

The Doctor goes back to the town and confronts Jex. The Gunslinger is a cyborg, part of an experiment that Jex had been working on. Jex says war had decimated his planet. He was given the task of ending the war, and an army of cyborgs did that within three weeks. The cyborgs were decommissioned at the end of the war, but one survived and started killing the scientists that created it. Two survived and fled to Earth.

Amy, Rory and Isaac discuss what to do with Jex. He is a war criminal, but did save the town and does not deserve to be executed. The Doctor disagrees and forces Jex out of Mercy. Amy tries to stop the Doctor, but the Doctor insists Jex has to face justice. Amy convinces the Doctor that they have to be better than Jex. Before he can move back into Mercy the Gunslinger appears behind him.

As the Gunslinger fires Isaac pushes Jex out of the way and gets hit, leaving the Doctor as Marshall of Mercy. The Gunslinger gives the people of Mercy until noon the next day to hand over Jex. Later that night a lynch mob tell the Doctor to walk away and leave Jex to them, but the Doctor manages to convince them that he can save them.

At noon the next day the Gunslinger meets the Doctor in the centre of town. They both stand facing each other waiting for the clock to finish chiming. When it does the Gunslinger fires up his weapon but the Doctor uses his sonic screwdriver to cause a distraction. Whilst most of the townsfolk are safe in church a number of people, with marks on their faces like Jex's, start running between houses to confuse the Gunslinger. He starts to walk around town and hears a noise in the church, and fires.

The Doctor tells Jex to go while he goes to the church. The Gunslinger finds the Doctor, but before he can fire he hears Jex transmitting from his ship. The Doctor tells Jex to leave so the Gunslinger will follow him and leave Earth. Jex knows that if he leaves the same thing will happen again as the Gunslinger will never stop pursuing him. Instead Jex activates the self destruct on his ship.

The Doctor, Amy and Rory leave Mercy, and leave behind a new protector - the Gunslinger.