The BBC Media Centre has released the official synopsis for the eleventh episode of the current series of Doctor Who, read on for further details:
DARK WATER - by Steven Moffat
In the mysterious world of the Nethersphere, plans have been drawn up. Missy is about to come face to face with the Doctor, and an impossible choice is looming. "Death is not an end" promises the sinister organisation known only as 3W - but, as the Doctor and Clara discover, you might wish it was.
Doctor Who: Dark Water will broadcast Saturday 1st November at 8:15pm on BBC One and BBC One HD.