Watch two new trailers for the third episode of series seven of, ‘Doctor Who: a Town Called Mercy.’

The Doctor gets a Stetson (and a gun!), and finds himself the reluctant sheriff of a Western town under siege by a relentless cyborg.

But who is he and what does he want? The answer seems to lie with the mysterious Kahler-Jex, an alien doctor (yes another one!) whose initial appearance is hiding a dark secret.

Watch the trailers below…