The Inmost Light is a short horror story by Welsh author Arthur Machen.
A scientist imprisons his wife's soul in a shining jewel, letting something else into her untenanted body, but the jewel is stolen.
Dyson was shocked at the result of his own audacity. The man shrank and shrivelled in terror, the sweat poured down a face of ashy white, and he held up his hands before him.
The story features the character of Dyson who occurs in a number of Machen's short stories. He is to all effects, an occult investigator. Here, he discovers the strange story of Dr. Black who lives on the outskirts of London. Black had a wife who mysteriously disappeared for an extended period of time, and was then witnessed staring demonically out from a window at the back of her house by Dyson himself.
He discovers, that she underwent a process of transformation whereby her soul was extracted into the confines of an opal, being replaced by that of a demon.
This scary story, like Dr. Jekyll & Mr. Hyde, wavers somewhere between horror and science fiction.
The Inmost Light was first published in 1894.
Arthur Machen (1863-1947) was a Welsh author and mystic of the 1890s and early 20th century. He is best known for his influential supernatural, fantasy, and horror fiction. His novella "The Great God Pan" (1890; 1894) has garnered a reputation as a classic of horror (Stephen King has called it "Maybe the best [horror story] in the English language"). He is also well known for his leading role in creating the legend of the Angels of Mons.