Well, it’s time for another serial where the Doctor and his companions come upon some aliens who don’t realize that they’re being used by another group of aliens.
These usually work out.
We start our story on an unnamed planet where the Gonds, a race a human-types, are selecting the best and brightest of their young adults to become companions to the Krotons, a mysterious race that lives in a giant machine. One guy, the son of the leader (another fun Doctor Who trope!), named Thara thinks the whole thing stinks since the companions never come back. He’s shouted down in the underground caves the Gonds call home.
Meanwhile, the TARDIS arrives outside. The Doctor comes out to look around with Jamie and Zoe. He’s got an umbrella because, as he explains to his own companions, the planet has a double sun and will get quite hot out when those things come up. The trio finds a large machine or building but take cover when a door opens. Out walks the male Gond that the Krotons selected, and some nozzle pops out and vaporizes the dude.
So, yeah, that tells the Doctor that something is wrong, and it doesn’t take long for the three of them to get inside to find the Gond prepping the other Kroton companion, a woman named Vana. Given how this show works, I wouldn’t be surprised if Thara is sweet on Vana, but as soon as the Doctor realizes what’s going on, he and his own companions jump in to stop the Gond. That actually leads to Jamie wrestling a guy to the ground. Considering what follows from the looks of things, it sure is nice to see Jamie get something down.
Anyway, Vana does go out, but the Doctor manages to get to her before she can be vaporized, and he sacrifices his umbrella as a shield to save both of them. It was his favorite. The Krotons will pay for that!
Once back inside, the Doctor learns what’s going on. The Gond believe the outside was poisoned by a nasty war many years before. The Krotons live inside the machine and run some learning machines that teach the Gond stuff. Every year or so, the Krotons choose the two brightest Gond to leave the Gond forever as companions to the Krotons. Seeing as how the outside is no longer toxic and it sure looks like the Gonds selected never come back for a very good reason, the Doctor sees this as a form of slavery.
Thara takes it less well and tries to smash the learning machines with some rowdy friends.
And then the Krotons speak. We still don’t see them, but we hear them. And they aren’t happy and send some kind of probe out, And what does the probe take a good look at?