The Terror (1963)

In 1806, André Duvalier, a French soldier lost in the Confederation of the Rhine, is saved by Helene, a young woman who bears a resemblance to Ilsa von Leppe, the late wife of Baron von Leppe who had died 20 years earlier. André sets out to investigate Helene's true identity and learns the Baron's darkest secret: after he found Ilsa with another man, the Baron killed his wife while his servant killed her lover.

Over the preceding two years, the Baron has been tormented by Ilsa's ghost, who has besought him to kill himself so that they can be together forever. After much hesitation, the Baron decides to do so and atone for his crimes. Unbeknownst to him, Ilsa's ghost is being commanded to haunt him by a peasant witch named Katrina.

After preventing the Baron from killing himself, André and Stefan, the Baron's majordomo, capture Katrina and force her into compliance. Katrina reveals herself to be the mother of a man named Eric, who she believes was killed by the Baron 20 years earlier. She hopes to avenge Eric's death by damning the Baron's soul to Hell. Stefan reveals that it was the Baron who had died, not Eric, and that Eric felt so guilty about it that he took the Baron's place (thus explaining why the Baron had never left the castle in 20 years). Over the years, Eric has convinced himself that he is truly Baron von Leppe.

Realizing her error too late, Katrina goes with André and Stefan to stop Eric from flooding the castle crypt. Katrina's deal with the Devil, however, makes her unable to walk on consecrated ground and she ends up burning to death after being struck by lightning.

At the von Leppe castle, Eric floods the crypt as Ilsa's ghost attempts to kill him and Stefan struggles to stop her. By the time André gains access to the crypt, it is already starting to cave in and he is only able to save Helene. The two share a moment outside the castle before Helene rots away into a skeleton.