Walter Kurtz is a fictional character from the novella "Heart of Darkness" by Joseph Conrad and its film adaptation, "Apocalypse Now." He is a highly skilled and respected Colonel in the U.S. Army who becomes increasingly unhinged during his mission in Vietnam. His descent into madness reflects the moral ambiguities of war and imperialism. In "Apocalypse Now," directed by Francis Ford Coppola, Kurtz is portrayed by Marlon Brando. The character embodies the dark side of human nature and the effects of isolation and power. His famous line, "The horror, the horror," encapsulates his realization of the brutality and chaos of both war and humanity.