Contrasting the women is the trio of Kurtz, Marlow, and the narrator. The triplet that binds the book is the various views of Africa from the adventure, economic, and religious standpoints.
The start of the book is set on the River Thames in England in contrast to where the journey takes place on the River Congo. The river acts as the path in for the Europeans allowing them entry to the inner Africa with out having to cross it, and furthermore giving them an inside perspective while the white man still is separate.
"Going up that river was like traveling back to the earliest beginnings of the world, when vegetation rioted on the earth and big trees were kings. An empty stream, a great silence, an impenetrable forest." (Conrad 59).
The action of travel upriver is another instance of the African environment trying to halt the progress of the whites while traveling downstream gives them a quick way out of the "darkness" and back to civilization. This alludes to Kurtz and his "choice of nightmares.".
"The brown current ran swiftly out of the heart of darkness, bearing us down towards the sea with twice the speed of our upward progress; and Kurtz's life was running swiftly, too, ebbing, ebbing out of his heart into the sea of inexorable time. . I saw the time approaching when I would be left alone of the party of 'unsound method.'"(Conrad 109).
Drawing from the text the river may be concluded to be an image of a demon or a snake threatening all who it may entrap.
"A mighty big river, that you could see on the map, resembling an immense snake uncoiled, with its head in the sea, its body at rest curving afar over a vast country, and its tail lost in the depths of the land." (Conrad 22).
The life and times of Kurtz serve as a valuable lead into the evil that is man. The Congo overtakes Kurtz on his journey to capture the ivory market. He goes from the products of European civilization and becomes victim to his barbaric instincts as his dark side reveals itself through partaking in horrendous rituals of the natives.