When Marlow tells his fellow sailors about how difficult it is to fully capture the truth through storytelling, Conrad reinforces his point through dramatic irony. Marlow says:
“I do not see [Kurtz] in the name any more than you do. Do you see anything? It seems to me I am trying to tell you a dream—”
[...]
“Of course in this you fellows see more than I could then. You see me, whom you know....”
Then, the sailor who narrates the novella continues:
It had become so pitch dark that we listeners could hardly see one another. For a long time already he, sitting apart, had been no more to us than a voice. There was not a word from anybody.
This situation is ironic because Marlow thinks that the other sailors can see him in the dark—which is a metaphor for them understanding his story—but they really can’t. Through this dramatic irony, Conrad suggests that Marlow’s message isn’t getting across: his audience (and the reader) misunderstands the true point of his story, even though he thinks they grasp at least part of it. This is significant because Marlow has just discussed Kurtz for the first time in his story. At this stage, the sailors (and readers) likely expect that Kurtz will live up to all the praise that others are offering him, and thus redeem European colonialism in the process. But he doesn’t, and when reality dashes Marlow’s expectations at the end of the novella, Marlow also dashes those of his audience. Thus, the subject of Marlow’s monologue adds another layer of irony to the situation: he thinks his audience is taking the hint about Kurtz being a disappointment, but they don’t—which sets them up for a far greater disappointment at the novella’s conclusion.
Because Marlow calls Kurtz an enigma at the same time as he is literally invisible to his audience, this dramatic irony also draws a direct parallel between Marlow and Kurtz. By describing Marlow as “no more to us than a voice,” the Narrator also foreshadows Marlow and Kurtz’s meeting, when Marlow encounters the dying, maniacal Kurtz as nothing more than a disembodied, invisible voice. In turn, this parallel suggests that Marlow plays a similar role for the other sailors as Kurtz played for him: he’s an enigma, a purveyor of tall tales so unusual that he becomes a mythical figure in his own right. This scene therefore suggests that the other sailors may not believe Marlow—and perhaps that the reader shouldn’t believe Conrad, either. In particular, readers should question the assumption that Marlow’s story accurately reflects Conrad’s real-life experiences in the Congo.
After Kurtz’s pathetic, miserable death, Kurtz’s Intended (his fiancée) continues to believe that he was a great hero, and Marlow can’t work up the courage to tell her the truth. The contradiction between her beliefs and the reality about Kurtz creates dramatic irony:
“‘No!’ she cried. ‘It is impossible that all this should be lost—that such a life should be sacrificed to leave nothing—but sorrow. [...] Something must remain. His words, at least, have not died.’
“‘His words will remain,’ I said.
“‘And his example,’ she whispered to herself. ‘Men looked up to him—his goodness shone in every act. His example—’
“‘True,’ I said; ‘his example, too. Yes, his example. I forgot that.’
Whereas Marlow and the reader know the truth—Kurtz spent his last years murdering native people for ivory, undermining his coworkers in the Company, and slowly going insane—Kurtz’s Intended still thinks of him as an idealistic crusader for truth and justice. Like many of the colonial administrators that Marlow met at the beginning of his journey, Kurtz’s Intended thinks that Kurtz’s words (like his pamphlet about the “Suppression of Savage Customs”) represent the best of European charity toward the rest of the world, and that his actions (going into the heart of Africa to civilize native people) set a glorious example for other Europeans.
Of course, she couldn’t be more wrong. In fact, the Intended’s specific claims add another layer of irony to this scene, because Kurtz’s words and example do live on—they just mean the opposite of what she thinks. His last words (“The Horror! The Horror!”) and the well-known postscript to his pamphlet about the need to civilize native people (“Exterminate all the brutes!”) stay with Marlow forever. Today, they are still widely known as symbols of colonialism’s brutality and corruption. Thus, Conrad uses dramatic irony in this passage to highlight the glaring contradiction between European colonialism’s stated goal (civilizing the world) and its true purpose (profiting through theft and conquest). Most Europeans only learn about colonialism from a distance, he suggests, and therefore continue to wrongly believe in this civilizing mission.