What’s the point of traveling through time and space if we can’t change anything?
You can be forgiven for thinking that John Lucarotti’s “The Aztecs” (Story Production Code F) is about the Doctor and his companions’ adventures amongst the Aztecs. An understandable mistake, because it’s about the Aztecs as much as Moby Dick is about a whale. Which is to say, yeah, of course, but not really.
No, “The Aztecs” is Doctor Who‘s first real examination of time travel and its limitations and potential paradoxes. The Aztec setting is really just window dressing, both scenic and moral, in this story, with endless parades of Aztec warriors processing back and forth whenever Barbara, mistaken for a reincarnation of Yetaxa, an Aztec High Priest, needs to go anywhere, and the issue of human sacrifice serving as the focal point in the Doctor and Barbara’s struggle about whether or not to intervene in history.
The action in the story revolves around the TARDIS materializing in an Aztec tomb with a one-way door that all of our intrepid time travelers manage to go through. This device of rendering the TARDIS inaccessible has been used in every story to date, save “The Edge of Destruction” and “The Daleks,” where the TARDIS was inoperable instead, a narrow distinction. Thus far in the series, the writers have not developed a story where the Doctor would want to stay in the setting and resolve the plot’s convolutions, and “The Aztecs” begins to give us some background about just why the Doctor doesn’t wish to meddle.