The episode opens with a recap of Hartnell’s very fluffed lines at the end of Inferno. ‘Dragged down to what,’ asks Ian. We then cut to a sci-fi planetscape with moons and constellations in the sky, which looks like it’s come straight from the cover of a Doctor Who Annual. The TARDIS materialises, and the roaming camera rather neatly switches to a view on the scanner screen. The interior of the Ship is much bigger this week as well (with a new science station bit in one corner, and a little medical bay), and everyone has changed costumes and hairstyles.

We cut back to the extraordinary spectacle of two chirruping ant creatures scampering about the space environment. Hartnell seems to be in a scampering mood as well. Considering that some sort of powerful force has caught the TARDIS, and Vicki has collapsed – quite unlike her normal feisty self – his giggly old man act seems a bit misplaced for once.

While, Barbara and Vicki have quite a sweet conversation about Vicki’s childhood, the Doctor and Ian go exploring the planet’s surface. There’s a neat echo and ‘glow’ effect that does help to make this feel like one of the oddest environments the TARDIS has ever visited. The Doctor remains resolutely high-spirited though, as concerned about the disappearance of Ian’s pen as the disabling of the Ship, and rushing about full of beans but apparently devoid of sense. It’s a thoroughly strange choice for Hartnell to play it so silly (is it all meant to be part of the discombobulating effect?), and it’s only William Russell doing his best to look foreboding that gives these scenes any drama.

The Doctor and Ian discover a vast pyramid, then the Doctor bizarrely instructs Ian to take his belt off, prompting the funniest line of the episode:

Ian: I hope my pants stay up.

Doctor: Yes, well that’s your affair not mine.

The escalating weirdness ends in a thoroughly disconcerting sequence of Ian tangled in some sort of net; a hypnotised Barbara striding through the landscape; swooping shots of the surface as Vicki desperately tries to escape in the TARDIS, and the Doctor, finally showing some sense of urgency as he realises the Ship has gone. It’s a queasy end to the most thoroughly outlandish episode yet.

Next episode: The Zarbi