The first stop on their quest to recover the keys of Marinus takes them to Morphoton. It’s a place where every whim and request is able to be indulged – although if this seems too good to be true it’ll probably comes as no surprise to learn that it is.

This episode is notable for having more edit points than was usual at the time – this was in order to demonstrate the difference between Barbara’s viewpoint (she can see their room for what it is – dirty and bare) and the others (they’re conditioned to view it as opulent). In later years this would be a scene that wouldn’t be at all remarkable, but when watching sequentially it’s another of those small moments which does stand out.

It’s maybe right that Barbara – the voice of reason – should be the one not to fall under the spell. But this wasn’t through any demonstration of free will, it was only because the conditioning disc placed on her forehead slipped off during the night. Note to the brains of Morphoton – it might be better to find a more effective way of conditioning your subjects (or at least use better glue).

The episodic nature of the serial means there’s not really time to develop the horror of Barbara being totally isolated.  She’s the only one of the four to retain her own memories (the Doctor, Ian and Susan have all been thoroughly brainwashed). This is a pity as the concept would have produced good material for several episodes. But there’s still the odd creepy moment, such as when Barbara rushes to the reassuring presence of Ian – but immediately after she’s embraced him it’s clear from his immobile stance that he’s no longer the man she knew.

We meet Altos (Robin Phillips) and Sabetha (Katherine Schofield). Both will join the others on the quest (Sabetha is Arbitan’s daughter and Altos is one of Arbitan’s couriers). Their presence is a good thing, especially as Billy’s shortly off for a two-week holiday. They’re fairly stock Terry Nation characters, so how well they come across depends on the actors (who do the best they can).

The brains of Morphotron are a little disturbing (especially the way they’re voiced by Heron Carvic) although the black and white picture does rob them of some of their impact. Barbara saves the day by smashing their brain cases and killing them. Or, at least, that was how it was scripted – alas, Jacqueline Hill only managed to smash one of the four cases and there was clearly no time for a retake. Oh well.

The Doctor’s decided to nip ahead and look for the last key (so we won’t be seeing Hartnell for a few weeks) whilst the others head to their next destination.

And it’s a Terry Nation favourite – a dangerous jungle!