What Influence does the setting have on the events and characters in the book?

The novella starts out in London. Marlow is already a world traveler when he takes a job as a captain of a steamboat destined to travel down the Congo River in Africa. Marlow finds London dark but not in the same way as discovers the Congo. Here he describes the river leading, "to the uttermost ends of the earth." Marlow is a seasoned seaman but the Congo is like another planet to him. Its inhabitancy is nothing like he had seen before. There is an "otherness" about them from the beginning. Marlow is horrified by places like the Grove of Death where people, no longer able to work, waste away. Marlow is also horrified at the callous disregard the colonies have for the inhabitants. The title of this book is very apt for the setting and its effect on Marlow. The Congo is full of indigenous people who look at the foreigners with vacant stares or anger. Indeed, many of them are cannibals which Marlow fears he might one day accommodate. The Congo is a place of foreboding but there is juxtaposition. Marlow concludes, by the end of the novel, that the heart of darkness is not so much the setting but the darkness inside the hearts of the Europeans who colonize the place.