I find this one kind of interesting, partly because it puts Barbara on a really cool pedestal for the serial as a high priestess of the Aztec civilization and partly because it’s the first one I really feel like asks the question “can we as the Doctor and his companions change history?” in a way that isn't like with the Tribe of Gum.

The answer is, well… no. Which makes sense, but it’ll be neat to revisit this stance on the idea between this serial and the point where Donna Noble accidentally renames gravity to be “mavity.” I feel like this could have moved a little faster like The Keys of Marinus did, but for a four-part serial it’s alright.