Dark allegory describes the narrator's journey up the Congo River and his meeting with, and fascination by, Mr. Kurtz, a mysterious personage who dominates the unruly inhabitants of the region. A masterly blend of adventure, character development, and psychological penetration. Critics consider this to be Conrad's finest, most enigmatic story.

The novella has been adapted for the screen numerous times, including Francis Ford Coppola's retelling, Apocalypse Now.