Galaxy 4 is one of the unfortunate lost serials from the early years of the series. So far there are only the audio files, which have been released on narrated CD by the BBC, and a few film clips appearing on the Lost in Time DVD. Together they convey the moral that beauty is in the eye of the beholder. The chumblies are the machine servants of a species called the Rill, a monstrously hideous alien race. The Doctor and his companions are rescued from the chumblies by a gorgeous race of warrior women called the Drahvins. Maaga, the Drahvin leader, informs them that the evil Rills caused them to crash on the planet and killed one of their number. Furthermore, the planet is in its last days before disintegration. But Maaga has a plan to capture the crashed Rill ship, which is in better condition, and escape. For this plot to work, she needs The Doctor's help.
Needless to say, not all is as it seems. They learn that Maaga is the only one of the Drahvins who can think independently. The rest of these gun-toting supermodels are emotionless cloned soldiers. There are only enough men on their homeworld to breed officers, the surplus exterminated. Maaga also has an uneasy air of violence and mistrust about her. This is so pronounced that she fires on a chumbly robot approaching their ship, explaining that the Rills use them to disseminate a lying offer to escape the planet together. When The Doctor offers to use his own equipment to determine if the planet is going to explode like the Rill say, Maaga holds back Vicki as a hostage. Then when Vicki and The Doctor go to reconnoiter the Rill ship, Steven is withheld.
By this point, about one and a half episodes into the four-episode run, the plot is telegraphed. The Rills did shoot down the Drahvin ship... after the Drahvins fired on them. As for the dead Drahvin, she was injured and the Rills sent out chumblies to help her. Maaga came along, fought off the chumblies, and then killed the injured crewwoman herself. She asserted that the Rills were "responsible" for her death. Their offer to bring the Drahvins with them on their ship was sincere. The Rill come from a planet devoid of conflict whose inhabitants communicate telepathically. Vicki learns all this when she is captive in the Rill ship, having seen the horror of the creatures for herself. Yes they are hideous, but that does not make them any less intelligent or benevolent.
This heartwarming story ends as one might imagine, with everyone learning not to judge a book by its cover and that leaving people to die on an exploding planet is okay if they're bad. The TARDIS escapes in the knick of time, sending its passengers back to Earth in those days already ancient when Homer wrote about them.