This is a lovely little conflict-free initial situation. Although with comments like "morituri te salutant" ("we who are about to die salute you"), we have a feeling there’s some conflict coming soon.
Marlow, upon hearing about Mr. Kurtz, almost immediately becomes obsessed with learning more about him and eventually with meeting him. To Marlow, Kurtz represents resolutions to many of the problems of the interior – eerie silence (by having an eloquent voice), the shenanigans of the native Africans (by "taming" them), the chaos of the wilderness (by bringing order with his acquisition of ivory), and the moral ambiguity of the interior. To some extent, Marlow sees himself reflected in Kurtz. The conflict lies in the perilous journey – both physical and spiritual – that Marlow must take to find the mysterious Mr. Kurtz.
As he journeys, Marlow discovers that Kurtz is not very well-liked, though he is universally respected. The manager, his uncle, and the brickmaker all have designs on moving up within the corporate hierarchy of the Company – and Kurtz’s success has put a crimp in their plans.
Then, there is the slight problem of Kurtz being utterly mad. He orders the attack on Marlow’s steamboat because he does not want to leave the interior. Marlow finds it difficult to relate to Kurtz in his present state. Also, the native Africans don’t want Kurtz to leave either, which nearly brings the pilgrims and the Africans to violence.
Kurtz tries to escape from his hut right before Marlow and company are scheduled to bring him home. Marlow chases after him. Marlow, at this point, has Kurtz’s fate in his hands. He can either let him go and allow Kurtz his victory, or he can follow Company orders and bring him back. Kurtz is too physically weak to resist either way. Marlow opts to ignore Kurtz’s ravings and carries him back. The next morning they make a successful escape from the restless Africans. And it’s all very climactic.
Kurtz dies. Suspenseful enough? In fact, he dies in complete agony, first going blind, then raving incomprehensibly, then finally seeing visions as he expires. His last words – "The horror! The horror!" – pronounce his final judgment on his world.
Marlow returns safely to Belgium, only to find that everything is petty and small when compared to the horrors he experienced on the Congo. He is also haunted by Kurtz’s letters, which he left to Marlow. Marlow decides to return the letters to Kurtz’s Intended.
Even after all the atrocities Kurtz committed and suffered, he is still remembered as something of a saint and martyr. The Intended makes this clear to Marlow as she goes on and on about adoring Kurtz, loving him, and his greatness. She sees his death as a loss not only to herself, but to the world at large. Marlow, the only man who saw Kurtz for what he truly was, is appalled but does nothing to correct her. In fact, he lies to her to preserve her idealistic illusion of the man.