This era of Doctor Who seems determined to create as many new little waddling robots with silly voices as possible. The croutons… sorry, I mean the Krotons, are supposedly crystalline metal ‘creatures’ rather than robots as such, although the science is fuzzy, and they basically are robots, complete with claw-ended tube arms and deadly acid gas guns. Also one of them sounds South-African for some reason.
A thousand years earlier, they conquered the planet’s inhabitants, the Gonds, and now they rule over them, forever unseen, hiding in the machinery underneath the Gond city. Now ruled as ‘gods’, they control the Gonds through lies and brainwashing, telling them that the wasteland outside is uninhabitable, and regularly selecting the most gifted candidates to join them as companions. What they’re actually doing once inside the machine is absorbing their brain waves to power their ship and then killing the unfortunate person afterwards with their deadly gas, which dissolves them into nothing.
Such a delicate balance of lies obviously doesn’t take much to upset, and the Doctor’s arrival immediately raises questions and shatters the Gonds’ faith. This causes an uprising, forcing the Krotons to come out of hiding and accelerate their plans. The Doctor and Zoe have sufficient mental energy to fully charge their spaceship (poor Jamie doesn’t), but using some hastily made sulphuric acid, the Doctor manages to dissolve the Krotons and destroy their ship, freeing the Gonds, and teaching them a bit of chemistry in the process.
This was another ‘unseen enemy’ type story, with rather bleak ramifications. Nonetheless, the Doctor has some comedic moments, exclaiming “great jumping gobstoppers!” and “oh my giddy aunt!” at one point. Gotta love him.