A Town Called Mercy (S07E03)

In "A Town Called Mercy," the Doctor dons a Stetson and wields a gun as he unexpectedly becomes the Sheriff of a frontier town besieged by a relentless cyborg known as the Gunslinger. As the Doctor grapples with his new role, he seeks to uncover the truth behind the Gunslinger's motives. The key to this mystery appears to be Kahler-Jex, an alien physician whose enigmatic presence conceals a troubling secret. As tensions rise, the Doctor must navigate the complexities of justice and morality in this perilous showdown.