While it's not historically accurate, Witchfinder General is a film about the life of Matthew Hopkins, a witch hunter in 17th century England. The horror represented in this story is real. Many innocent men and women were tortured during this time period until they "confessed" to being witches. Then they were summarily hanged. This same kind of torture and murder was also seen in the United States as well, especially in Salem, Massachusetts.
Witchfinder presents the subject matter at hand with unflinching honesty. Vincent Price is excellent as Hopkins and embodies the role without his usual sense of camp. He portrays Hopkins as a man who had zero empathy for his victims and was sadistically cruel to those he tortured. Powerful stuff! The rest of the cast is very good as well and help convey the brutality of the subject matter in a way that rings true.
The sets and costumes are great and look like the kind of stuff associated with Hammer Studios. It really adds to the enjoyment of the film. The direction and cinematography are spot on as well.
Don't miss this one. It's not one of Price's best known films but it should be. Furthermore, if you find the subject matter interesting then also check out the 1922 Danish silent film Haxan which can be rented through Netflix. It's my personal favorite on the subject of witchcraft and the unfortunates that were accused of practicing it.
For more info check out the episode's entry in IMDB.