The film’s use of the Yoruba religion distinguishes it from being a copy of the Exorcist with a black cast. In the story, Abby is apparently possessed by Eshu, a West African orisha of chaos and whirlwinds. He is also a trickster and the guardian of roads, particularly crossroads.
In the opening scene of the film, Dr. Garrett Williams (William Marshall) explains to his students, “Eshu is the most powerful of all earthly deities. Eshu is a trickster, creator of whirlwinds… chaos.”
While on an archaeological dig in a cave in Nigeria, Dr. Williams finds a small, ebony puzzle box, carved with the symbols of Eshu: the whirlwind, the cock’s comb, and the erect phallus. When Dr. Williams discovers the mechanism to open the box and unlatches it, a tremendous wind blasts out, knocking Dr. Williams and his men against the cave walls and floor.
The spirit released by Dr. Williams crosses the Atlantic to Louisville, Kentucky to the new home of Dr. Williams’ son, Emmett Williams (Terry Carter) and Abby Williams (Carol Speed). Why and how the spirit travels the globe is not explained. After Abby becomes possessed, her behavior becomes exponentially bizarre and dangerous.
In the movie, the dialogue doesn’t specify whether the spirit inside Abby is Eshu. The plot’s final resolution leaves the point unclear. In And You Call Yourself A Scientist, Elizabeth A. Kingsley wrote “from a theological point of view, the final section of Abby is quite fascinating. Toward the end of the film, having spent some time taking the demon’s measure, Garret decides that it is not in fact Eshu, but a rather pathetic Eshu wannabe… who presumably was imprisoned by Eshu.”