This is an underwhelming conclusion to a story that started with such spooky promise. Somewhere along the way, an ‘icy suction’ (as Sarah describes it) descends and all the atmosphere disperses until we’re left with Prentis Hancock wildly gesticulating while Freddie Jaeger gurns inside a Top of the Pops disco effect. The simplicity of the central idea – Sorenson has taken something from Zeta Minor, and its guardian is hunting him down to get it back – is lost. It’s hard to even understand what’s meant to be going on in this episode, and even harder to care about it.

The problem is largely the script’s uncertainty about what exactly is happening to Sorenson, and why. He’s stolen some antimatter but is himself turning into a werewolf “anti-man”, but can hold off the change by taking a vaccine to protect against antiquark penetration except now the vaccine itself (?) has created a chemical change that means that Sorenson can duplicate himself into antimatter creatures similar to the one on Zeta Minor, and Salamar using an accelerator is really bad for some reason. The lack of clarity around this element of the plot, and that what it means in practice is Ewen Solon and Elisabeth Sladen running round corridors placing cones, results in a very confused and unfocused finale.

It’s a shame that this is so terribly weak. David Maloney continues to do his best – there’s a neat shot of all the ship’s hatchways closing in sequence – but I don’t really get any sense that he or the actors are entirely convinced by the material. I’d have enjoyed this more had Louis Marks gone for some mystery in who the antiman killer was – Sorenson was half mad from the get go, and is never interesting enough for the change to reveal something about his conflicted character. Instead, we’ve known exactly what’s going on and have spent the last fortnight waiting for Salamar and co. to cotton on. There’s a hint that the Doctor is trying to convince Sorenson to kill himself to save them all, which is dark. But the storytelling is so vague it’s hard to be certain. As a result of its botched second half, Planet of Evil is a misfire, albeit one that comes so close to being good.

Having lost interest in the story during Part Three, I’ve taken more notice of incidental detail. The idea of the Morestrans as another race of desperate survivors trying to survive the death of their sun links this thematically to so many previous Hinchcliffe and Holmes stories. I’m also wondering whether there’s a conscious effort underway to make Sarah Jane a bit softer. She’s out of the trouser suits, Scandi jumpers and leather jackets she usually wore and in flouncy frills, and her hairs got very bouncy. She’s definitely much more glam than she used to be. She’ll be going full-on 1970s Edwardian retro next.

Next episode: Pyramids of Mars