Most of Heart of Darkness consists of Marlow telling his story to a group of other sailors. Even though the novella never puts the reader directly inside Marlow’s mind, his free-wheeling storytelling technique still brings his stream of consciousness to the foreground. It makes the story’s structure largely psychological: rather than unfolding in linear time, the narrative mostly follows Marlow’s thoughts, feelings, and perceptions. Marlow comments at length on individual moments that he considers significant, while often skipping over days or even months of his journey in less than a sentence. For instance, while describing his meeting with the Russian, he recalls:
The glamour of youth enveloped his parti-coloured rags, his destitution, his loneliness, the essential desolation of his futile wanderings. For months—for years—his life hadn’t been worth a day’s purchase; and there he was gallantly, thoughtlessly alive, to all appearances indestructible solely by the virtue of his few years and of his unreflecting audacity. I was seduced into something like admiration—like envy.
Because Marlow is telling his own story in real time, his narration focuses less on his actual conversation with the Russian than his feelings about the Russian. Indeed, because of Marlow’s narrative style, his encounters with men like Kurtz and the Russian say far more about him than about these other men. This adds to the novella’s psychological drama by emphasizing how Marlow’s experiences have changed him. For instance, his envy for the “gallantly, thoughtlessly alive” Russian is significant because it underlines how his experience with the Company turned him into a cynic: he once dreamt of exploration and discovery (but no longer does), and he envies how the Russian keeps that dream alive. Readers cannot know if these were Marlow’s immediate thoughts upon meeting the Russian, or if he’s adding them into his story after the fact. But this is actually Conrad’s point. Since one of the novella’s major themes is that it’s impossible to ever fully know someone else—or oneself—Marlow’s testimony challenges the reader’s attempts to discern what really happened, or whether he really feels everything that he’s telling the other sailors.
Conrad also uses Marlow’s stream-of-consciousness storytelling style to build suspense over the course of the novella. At the beginning, there’s a clear mismatch between Marlow’s dark, cynical tone and the innocuous story he starts to tell about working for the Company. For instance, when describing the moment he first reached Africa, he hints at the dangers that awaited him by mentioning a “general sense of vague and oppressive wonder.” But, over the course of his story, Marlow’s experiences start to explain his cynical comments and digressions: he is clearly haunted by what he has seen, but readers will not have a chance to see it themselves until they meet Kurtz at the end of the book.