We follow a king‘s Doctor in one kingdom & a ruler‘s Bodyguard in another on an alien planet still in its Medieval era and examine their inverted philosophies.
It‘s never explicitly stated that the Doctor and the Bodyguard are secretly members of the space-faring wildly-technologically-advanced Culture but, yeah.
Slow-going for awhile, but the gut-punch Banksian twists at the end did not disappoint.