The man they arrested last time turned out to be the Spanish ambassador.
One can hardly accuse Malcolm Hulke of burying the lede in “Colony in Space” (Story Production Code HHH)—the very first scene features the Time Lords fretting about the Master, who has discovered the site of a buried Doomsday device. And yet we hear no more of this ominous development for four episodes, during which the Doctor deals with an entirely different set of difficulties involving colonists on an infertile planet and a greedy mining corporation bent on taking the planet from them.
Watching Doctor Who as one does now, with all the episodes available immediately, the omission seems strange, as a Doomsday device should ostensibly be the focus of the story rather than poor cover crop yields and bountiful durilinium deposits. But at the time, when viewers had the show parceled out in weekly chunks, the surprise when the Master is finally revealed carries with it the frisson of remembering that moment from the beginning of the first episode, obscured as it was by the intervening action.
It’s certainly not the first time that the Master’s appearance has been teased; “The Claws of Axos,” immediately prior to this story, similarly featured the Master showing up in the middle of the action after his appearance had been suggested at the very beginning of the first episode. In that story, however, the Master was directly connected to the appearance of Axos on Earth and thus to the main thrust of the plot; in “Colony in Space,” he shows up opportunistically, his story arc only tangentially connected to the central plot. Hulke has, essentially, smashed two stories into one here, either of which might have made for a decent story but the sum of the parts not adding up to much at all.
The colony arc that gives this story its title starts promisingly enough, with the Doctor and a slightly shanghaied Jo Grant being whisked off to the planet Uxarieus (a quarry, of course, but our first alien quarry-planet in color, one with a lot of mud) at the behest of the Time Lords, who send the TARDIS there so that the Doctor can defeat the Master’s plans. However, the Time Lords don’t actually tell the Doctor to expect the Master, either a signal vote of confidence in his abilities or a fear that he would reject helping them. (Or, perhaps, just a clever narrative elision to extend the story to six episodes.)
The Doctor immediately gets excited to explore the mysteries of why the colony is failing and, with unexplained murders happening right after his arrival, he’s drawn quickly into events, but just to be sure he sticks around, the TARDIS is dragged off by the voiceless “primitives” who are native to the planet. As if the Doctor would try to run away after he realizes that the murders were committed by a mining robot that has fake animal claws attached to it?