Dark Shadows (1966)

Season 4: Episode 90

Disturbed by her nephew's insistence that he is haunted by a ghost, Elizabeth Collins-Stoddard reluctantly agrees to hold a seance in her home. During the seance, the ghost, aka Sarah Collins, chooses to speak through the governess, Victoria Winters. However, the seance doesn't last long when Miss Winters suddenly disappears and a strange woman is found sitting in her place.