Before the Flood - Synopsis

The BBC Media Centre have issued the synopsis for the fourth episode of current series of Doctor Who:

BEFORE THE FLOOD - by Toby Whithouse
On a remote Army outpost, a fearsome alien warlord - the Fisher King - sets in motion a twisted plan to ensure his own survival. The ripples will be felt around the universe. Is this chain of events inevitable? And can the Doctor do the unthinkable?

Doctor Who: Before the Flood will broadcast on Saturday 10th October at 8:25pm on BBC One and BBC One HD.