Civil War veteran Josiah Grey comes to a small town to be a gospel minister. In time he has a family and many friends, but he also finds friction with a few of his parishioners. A young doctor grates at what he feels is the parson's interference in the scientific treatment of patients, and a mine owner resents Grey's protection of an old sharecropper whose small plot of land stands in the way of his continued mining. Grey must face a public health crisis and a lynch mob as a result, all seen and described through the eyes and memory of Grey's young nephew John.

In 1903, Doctor Huntington Bailey meets a friendly older lady during a train trip. She tells him that she is going to visit her brother Nick and his lovely young wife Allida. Once in New York, Bailey hears that his train companion suddenly died. Shortly afterward, he meets the strange couple and gets suspicious of Nick's treatment of his wife.

American psychologist John Holden arrives in London to participate in a symposium aiming to expose witchcraft and devil-worship as a fraud, with attention centered on a cult run by a Julian Karswell. Debarking his plane, Holden learns that the symposium leader, Henry Harrington, has suddenly died and he is now in charge. What only the audience knows is that Harrington was clearly killed by a demon, apparently summoned by Karswell to avenge his persecution. Despite both threatening and cajoling behavior by Karswell, Holden determines to proceed, though the only cult member willing to talk about his experiences is in a prison psychiatric ward, catatonic after allegedly killing yet another cult member. However, Harrington's niece, Joanna, believes, based on her uncle's notes, that Karswell may indeed have some satanic powers derived from an ancient tome in an obscure language which he has been able to translate, and attempts to warn the skeptic Holden. Karswell's mother also attempts to warn Holden off. However, the thing which begins to most get to Holden are the occasional, but mounting, sensory and mental disturbances he begins experiencing after an encounter with Karswell, and the discovery that, during this encounter, Karswell secretly slipped a slip of parchment with a curse in runic symbols on it into Holden's belongings, a parchment identical to one Harrington recorded having had passed to him in a similar manner shortly before his death... [N.B. Holden at no point stays at the Karswell estate].

A chance discovery leads American mining engineer Ben Harris and acquaintance Harold to discover a lost city under the sea while searching for their kidnapped friend Jill. Held captive in the underwater city by the tyrannical Captain (Vincent Price), and his crew of former smugglers, the three plot to escape...

A young Canadian nurse (Betsy) comes to the West Indies to care for Jessica, the wife of a plantation manager (Paul Holland). Jessica seems to be suffering from a kind of mental paralysis as a result of fever. When she falls in love with Paul, Betsy determines to cure Jessica even if she needs to use a voodoo ceremony, to give Paul what she thinks he wants.

When the naval construction designer Oliver Reed (Kent Smith) meets the Serbian Irena Dubrovna Reed (Simone Simon) in the zoo, he flirts with her and they sooner fall in love and marry each other. However, Irena is afraid of an ancient course of her town that women can not be touched by a man, otherwise she will transform in a panther, and the couple does not consummate their marriage. Irena is sent for treatment with the psychiatrist Dr. Louis Judd (Tom Conway), while Oliver looks for "consolation" with his colleague Alice Moore (Jane Randolph). When Irena sees that she is losing Oliver to Alice, she becomes jealous and hateful, leading to a tragic end.

Jeff Bailey seems to be a mundane gas station owner in remote Bridgeport, California. He is dating local girl Ann Miller and lives a quiet life. But Jeff has a secret past, and when a mysterious stranger arrives in town, Jeff is forced to return to the dark world he had tried to escape.