Not so many thoughts on the murder, but lots of backstory.
So – Conwy Wales and Lland-whatever that’s across the bridge.
The necromancer poisoned the water supply with the plague virus. The team came in to stop the zombies and clean up. The magical adviser (and others) set up water filtration units, but he doesn’t know how long it will be until the virus is completely out of the water system. It got into the food that was growing and the animals. He could not tell if it affected the animals’ (horses, cows, sheep) intelligence. Maybe it made them more biddable. So all the food that he eats is purified in some manner (microwaved). He comes from a technological/mechanical future.
Or maybe it’s not the future that he comes from – it’s just that the entire country has forgotten how to use technology and people reverted to feudalism. Cars, airplanes, trains – all not in use. Microwaves, tvs, cell phones, stereo systems, ipods, etc., all useless. Maybe the government had the army destroy the media items because the necromancer (or terrorist group) was using that to broadcast its message of control.
There is a building in Conwy that houses all of the records of the people (library, tax service place) – where one could find out who one was before the war. For example, maybe the Captain was a soldier in the Welsh army and he was sent into the warzone to destroy technology and fight the afflicted citizenry. He could have had a family – and he doesn’t remember them. He knows he’s a soldier, he was in the war and fought zombies, and now he’s in charge of the town’s defenses.
And of course the uber government (not the local Lord/Baron whomever) is out to cover things up – and encourages the feudalism, as long as it gets its tax money and the people are under control. Just until the virus is cleared up and the last of the terrorists are captured/put down. Uh-huh, sure.
Technology that still works runs on magic. Whether that magic is real magic or just seems magical because people don’t know better/understand it is unknown. Something about the virus and the antidote (sprayed from airplanes by the uber government) created a fundamental change. There is magic in the world now.