The Android Invasion is another Doctor Who version of a widespread science fiction trope, this time the replacement of people in a sleepy village with robot replicas. In this case, however, it turns out that not only the people but the entire village has been replicated.
The symbolism as the Doctor notices a calendar in the village is made explicit by his comment. As he sees that the calendar only has July 6th, he says, “A village without a future.”
As one would expect, aliens are behind it. In this case, a species known as Kraals, who are persuaded that science will give them victory. They want to unleash a virus that will destroy humans.Stories of this sort inevitably play on our fear that someone who seems like a friend could be an enemy. This is highlighted not only through the robot duplicates, but also an astronaut named Crayford whom the Kraals rescued, and whom they then deceive and manipulate into helping them. But when he realizes their plan, he turns against them.
Given that this is a well-worn type of story, I think that this Doctor Who episode manages to do a good job of keeping it as fresh and interesting as possible.