Having previously betrayed UNIT to return the world to a golden age, Mike Yates goes to a meditation centre for peace of mind however, finding more than he bargained for, he brings along Sarah Jane to look into the place. Meanwhile the Doctor investigates ESP with someone gifted in this way. Both parties come together when they find connections to a blue crystal, and the intergalactic ambitions of a load of spiders on the planet Metebelis 3.
This is the last serial featuring Jon Pertwee's Doctor and in some ways it should be commended for its restraint because, as Theo Robertson observes, if this was the modern series then a regeneration would have to feature every creature from the series, at least 2 former companions, and several kitchen sinks. Planet of the Spiders doesn't go all out to be anything particularly different for its finale, but it does actually make an effort in one way – which is to deliver almost a potted summary of Pertwee's tenure. So the plot involves ideas, monsters, human corruption or moral weakness, martial arts, chases, bloody stupid vehicles, UNIT, and as ever – villains who are able to escape because nobody takes their keys when they get out of a vehicle. As a sort of tasters platter it is decent enough, but it has the weakness that all of the aspects do not work and, as is often the case with the 6-parters, it feels padded.
This is evident in some very weak "cliff-hangers" but can also be seen in other ways, such as an episode that is essentially one big long chase; sounds exciting but in reality it is comically silly. Speaking of which, the spiders really don't have the fear factor they should do – and I say this as one not a fan of them but yet totally unphased by events here. It does play out reasonably well, but it is always "okay" rather than really great. Pertwee himself is pretty good, although I didn't think again that Sladen had a great amount to do. Perhaps better is to come from her, but Sarah Jane is considered one of the great companions and being honest she has not made much of an impression on me yet, despite having had the whole season to do so. Good to see the regulars of UNIT back, and the main human villain (Dearth) was good.
All told, this eleventh season had its weaker moments, and generally after the first two serials it was not what it needed to be. This serial has a bit of everything for Pertwee fans before they refresh the production for season twelve. It doesn't all work and it does feel very padded out, but it is an enjoyable last go-around for Pertwee's Doctor, and his final moments of self-realisation and sacrifice are very well handled.