A murder mystery film set in a medieval village. After an outbreak of plague, the villagers make the decision to shut their borders so as to protect the disease from spreading (see the real life case of the village of Eyam). As the disease decimates the population, however, some bodies start showing up that very obviously were not killed by plague.
Since nobody has been in or out since the outbreak began, the killer has to be somebody in the local community.
The village constable (who is essentially just Some Guy, because being a medieval constable was a bit like getting jury duty, if jury duty gave you the power to arrest people) struggles to investigate the crime without exposing himself to the disease, and to maintain order as the plague-stricken villagers begin to turn on each other.
The killer strikes repeatedly, seemingly taking advantage of the empty streets and forced isolation to strike without witnesses. As with any other murder mystery, the audience is given exactly the same information to solve the crime as the detective.
Except, that is, whenever another character is killed, at which point we cut to the present day where said character's remains are being carefully examined by a team of modern archaeologists and historians who are also trying to figure out why so many of the people in this plague-pit died from blunt force trauma.
The archaeologists and historians, btw, are real experts who haven't been allowed to read the script. The filmmakers just give them a model of the victim's remains, along with some artefacts, and they have to treat it like a real case and give their real opinion on how they think this person died.
We then cut back to the past, where the constable is trying to do the same thing. Unlike the archaeologists, he doesn't have the advantage of modern tech and medical knowledge to examine the body, but he does have a more complete crime scene (since certain clues obviously wouldn't survive to be dug up in the modern day) and personal knowledge from having probably known the victim.
The audience then gets a more complete picture than either group, and an insight into both the strengths and limits of modern archaeology, explaining what we can and can't learn from studying a person's remains.
At the end of the film, after the killer is revealed and the main plot is resolved, we then get to see the archaeologists get shown the actual scenes where their 'victims' were killed, so they can see how well their conclusions match up with what 'really' happened.
