There’s a very creditable attempt to create a creepy atmosphere, as the Doctor and Romana spend most of the episode exploring the E-Space equivalent of Castle Dracula, discovering that it’s a spaceship (the kind of reveal that would have been the punchline in most series), that its storage bays are filled with drained corpses, the fuel tanks are being used to store blood, and that underneath, something vast waits for the Time of Arising.

It’s leavened by some jokes (the Doctor looking pained because Romana jumped on his toe), but the overall tone is closer to Hinchcliffe than anything since Image of the Fendahl. The Doctor implies that vampire legends across all inhabited planets have their roots in this reality: a last gasp of the ancient astronaut idea that provided so many of the memorable moments of the Seventies series. There’s a risk, given how much the series has moved on, that this could have looked a bit outdated – like doing Revenge of the Cybermen six years after Troughton. Instead, it feels almost like the fourth Doctor returning to his roots to face the last big classic horror monster he hadn’t defeated. His line, ‘I have a suspicion, but it’s too horrible to think about’ echoes The Ark in Space’s ‘It’s almost too horrible to think about’. I don’t think you could have got away with a whole series like this in 1980 (even Hammer House of Horror had moved on from the old monsters), but as a last hurrah for this type of story it’s very compelling.

The bulk of the episode is built around the Doctor and Romana’s investigations, but the few other scenes add seasoning to this: Aukon, who looks disconcertingly like JNT’s partner Gary Downie, is a truly grisly creation, grooming Adric as the Chosen One (‘The boy is still young. His mind is strong, clear, but malleable. We can make of him what we wish.’) and talking about the peasants as if they were livestock: ‘We have bred dullness, conformity, obedience into those clods for twenty generations.’ Ivo and Marta’s touching adoption of Adric as a replacement for their son is repaid by Adric being rude and arrogant. Is the sudden switch from night to day in the opening model shot meant to imply it took the Doctor and Romana all night to get to the tower, or that the nightfall as artificially summoned by Aukon?

Next episode: State of Decay – Part Three