Speaking exclusively to Digital Spy, writer Toby Whithouse said:
"Mine is the third part of a three-parter – Steven [Moffat]'s done the first one, Peter Harness did the second and I've done the third.The three-part story, which will take place across episodes six, seven and eight of the new run, will feature creepy new monsters in the form of The Monks as well as the return of Missy (Michelle Gomez).
"It's set modern-day... and I think anything more than that and Steven will come round and kick me in the shin!"
Doctor Who returns with series opener The Pilot on Saturday 15th April on BBC One.
[Source: Digital Spy]