The theme of the Double is one of the most fascinating elements of gothic fiction, carrying with it a whole catalogue of literary conventions: the reflected image in the mirror or in water, the identical twin, the changeling, the dead who possess the living, the unfettered subconscious, family madness, the Devil. All these apply to The Other, which is a vague term for some possibly metaphysical entity which imposes its will on one's consciousness or behavior, a presence never recognized as a part of oneself, although psychologists may call it a projection of forbidden impulses, perhaps the Jungian Shadow.

In medieval literature, the projected source of evil was often the Devil or the witch. Modern gothic novels are somewhat more circumspect, suggesting that devils are probably internal and human, perhaps devices for escaping personal guilt. Nevertheless, since the modern imagination has never given up its fondness...