When Marlow visited Kurtz's Intended, he had the vision of Kurtz and seemed to hear the whispered cry "The horror! The horror!" again. Why ?
Conrad was very interested in the contrast of “the raw and the cooked,” that is, the civilized vs. the primitive (Claude Levi-Strauss’ metaphor for the two stages of civilization). The whole experience of Kurtz among the “cannibals” of Africa is contrasted with the “civilized” world of Marlow’s homeland and the disciplined regimen of his sailing ship. When Marlow talks to Kurtz’s fiancé, where the refinements of formal marriage are manifest, Marlow is reminded of the contrast with the sexuality of the jungle, and the echo of Marlow’s moment of realizing the contrast is present through this device of Conrad’s. For the reader, the echo is a reminder of what the novel is about.