The BBC Press Office have issued the synopsis for "A Town Called Mercy" and "The Power of Three":
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, who goes by the name of the Gunslinger.
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.
Writer - Toby Whithouse
Executive producers - Steven Moffat and Caroline Skinner
Producer - Marcus Wilson
Director - Saul Metzstein
The Power of Three
The Doctor and the Ponds puzzle an unlikely invasion of Earth, as millions of sinister black cubes arrive overnight, almost like presents falling from the sky.
But what are they, what’s inside them and most importantly, who sent them? With the international community at a loss, it’s left to the Doctor to unearth who is behind the mystery.
Guest stars: Mark Williams, Steven Berkoff and Jemma Redgrave
Written by Chris Chibnall
Executive produced by Steven Moffat and Caroline Skinner
Directed by Douglas Mackinnon
Produced by Marcus Wilson
"A Town Called Mercy" airs on BBC1 on Saturday 15 September 2012 at 7.35pm. "The Power of Three" will air on BBC1 on Saturday 22 September 2012 at a time to be confirmed.