DRAMA. Head up! You really do not want to miss the start of this penultimate episode. By which I mean Scene One before the title sequence. It's a Big Moment. Say no more...

World Enough and Time marks the start of Steven Moffat and Peter Capaldi's farewell to Doctor Who, leading into next week's finale an on to the Christmas special. It's a deliciously macabre instalment, with several shocking incidents an a tone of despair that may disturb older viewers. You might need a young family member to comfort you.

The Tardis arrives on a mighty colony ship 400 miles long an 100 miles wide, which is trying to reverse away from a black hole. The gravitational pull means that time is running faster at the top of the vessel than the bottom. As part of her rehabilitation, Missy is answering the ship's distress call. With Bill and Nardole as her "plucky assistants", she delights in posing as "Doctor Whhooo!" (the fab Michelle Gomez giving the name some Glaswegian welly).

Moffat warned RT readers that the Doctor "witnesses the death of someone he is pledged to protect". But who will it be? Who are the hospital patients waiting in pain? And how does it all fit in with Missy's earlier incarnation (John Simm returning as the Master after seven years) and the original 1960s cloth-faced Cybermen? In short, riveting.

THE TWO MASTERS: What role will Missy (Michelle Gomez) an her earlier incarnation (John Simm) have in the downfall of Peter Capaldi's Doctor?