I'm glad they keep mentioning the quest to the find the Key of Time at the start of the first episodes, end of the last one, and once or twice in between, because otherwise I would forget since it really serves no real purposes as a narrative device. I presume it will start to come together as we proceed (and the mention here of a Black Guardian suggests a bigger villain will appear), but in this serial it is pretty meaningless as a concern. Instead the Doctor finds himself in modern day Cornwall where people are making sacrifices to Cailleach, the goddess of war and magic, at a megalithic circle known as The Nine Travelers. This is the start but it will lead to hyperspace, a trial, death sentences, and large mobile rocks which even K9 can barely stop.
As the end of that plot summary suggests, this is a bit of a messy serial but it is actually pretty solid. Maybe that is my lowered expectations for this season having an impact, but I quite enjoyed it despite it not really gripping me or doing too much to hold my attention. The serial is notable for its female characters in key roles; not just the number of them but also the positions they play. Indeed, I felt that the assistant role was a bit exposed because here the Doctor had a great 'peer' relationship with Professor Rumford, making me think she might be quite a fun assistant since she was smart but also too old to have time for any nonsense like silliness or screaming in a mini-skirt.
The plot is quite interesting as it mixes style. The first half is a bit old school English horror, whereas the second half jumps to the sci-fi realm and has quite a good trial which occurs. That said, it doesn't all hang together, and the cliffhangers don't really have much impact in terms of keeping the stakes up. The 'monsters' are fun, but not in an effective way so much as it is just plain enjoyable to see a big rock lumbering around the place (every child has fears of Daleks, or statues etc because of Dr Who, but I have never heard anyone scared of rocks because of the Ogri). The variety in the plot does keep it moving through, and I liked that action was spread around, and the serial had a progression so the pace was solid and it didn't feel like it was killing time (even some of the 4-parters can feel like this, like they are just putting characters into trouble for the sake of keeping them busy).
The cast is enjoyable and on good form, and the mix of location shooting, sets, and models all added to that varied feel. Stones of Blood is in no way a great serial, but it is a solidly enjoyable one, which is very welcome in this not particularly strong season.