Set in 1806, it is the story of a lost French soldier (Jack Nicholson) saved by a strange young woman named Elaine (Sandra Knight), who looks like Ilsa, the baron's (Boris Karloff) wife, who died 20 years ago.
Trivia
Clips from the film were used years later in the 1968 Karloff movie,Targets.
Leftover sets from other AIP films were also used, notably those from The Haunted Palace, a Vincent Price horror film made the same year. The tree against which Sandra Knight expires was the same one Price was tied to and burned in Palace.
Although credited to Corman, Francis Ford Coppola, Monte Hellman, Jack Hill and Jack Nicholson, all shot parts of the film. Corman shot footage of Karloff and other actors walking across the sets and down stairs with the belief that he would be able to make sense of them later. In the next three days Coppola, Helman and Hill all tried to do something. Nicholson, who was keen to get directing experience himself, also took a turn behind the camera.
The film was also released as Lady of the Shadows, The Castle of Terror, and The Haunting.
Actor Dick Miller, who plays Karloff's major domo, was hired to shoot new scenes in the early 1990s to use as framing sequence for an overseas version of The Terror. Under this scheme, the main action of the film is presented in flashback.