Enhanced descriptions from Syndetics:

Heart of Darkness is a novella written by Joseph Conrad. Before its 1902 publication, it appeared as a three-part series (1899) in Blackwood's Magazine. It is widely regarded as a significant work of English literature and part of the Western canon.The story details an incident when Marlow, an Englishman, took a foreign assignment from a Belgian trading company as a ferry-boat captain in Africa. Although Conrad does not specify the name of the river, at this time Congo Free State, the location of the large and important Congo River, was a private colony of Belgium's King Leopold II. Marlow is employed to transport ivory downriver; however, his more pressing assignment is to return Kurtz, another ivory trader, to civilization in a cover up. Kurtz has a reputation throughout the region.This very symbolic story is actually a story within a story, or frame narrative. It follows Marlow as he recounts, from dusk through to late night, to a group of men aboard a ship anchored in the Thames Estuary, his Congolese adventure. The passage of time, and the darkening sky, during the fictitious narrative-within-the-narrative parallels the atmosphere of the overall story. (wikipedia)