A young girl, Juanita, finds her parents killed in a voodoo ritual on a distant tropical island. She escapes with her life, but when she reaches adulthood, she feels compelled to return to the island, bringing her daughter and nanny with her. Once there, she goes to stay with her uncle who lives on the island. She soon discovers that the natives, who had been using her for voodoo rituals when she was a child, now treat her as a voodoo goddess. In this role, she begins leading their rituals. Any attempt to fight Juanita's influence or to remove her from her position is met with violent force. One person is found dead in a lava pit, while another is found hanged. At one point, Juanita is so overcome by the voodoo curse that she offers her daughter up for sacrifice. Juanita's businessman husband, Stephen, follows her to the island and attempts to travel into the jungle to rescue her, but finds her taking part in a sacrifice of an innocent woman. Although he shoots the high priest of the tribe, Juanita completes the sacrifice herself. Their high priest injured, the natives now plan to murder all of the white people on the island. Stephen takes his daughter and two others into the fortified section of a plantation house. The natives succeed in capturing Stephen and his secretary, Gail, but they are eventually rescued. In the end, Stephen shoots and kills Juanita just as she is about to sacrifice her own daughter.
In their 1934 review of the film, The New York Times wrote: "Black Moon, although it is strictly studio-made, is admirably equipped to throw a double-bar-relled scare into the innocent entertainment-hunter." James Jay Edwards of FilmFracture gave the film a mostly positive review, commending the film's downplaying of "stereotypical conventions" associated with the voodoo horror sub-genre, while also noting the predictability of the film's antagonists. Edwards concluded his review by stating, "While not one of her more iconic performances, Black Moon is still an impressive film about voodoo zombies, sans the zombies." On his website Fantastic Movie Musings and Ramblings, Dave Sindelar commended the film for its "brooding atmosphere", unpredictability, and Muse's performance; while also noting the film's unevenness, and Wray's character existing "more for the sake of convenience than for anything else".
