Marlow tells a story on a boat at the mouth of the Thames: he once traveled up the Congo to find Kurtz, a brilliant ivory trader who has become something monstrous. Conrad's 1899 novella is about colonialism, about the darkness inside civilized men, about what happens at the edge of the map. 'The horror' is Kurtz's last judgment, and critics have argued ever since about what he means. Achebe famously called the book racist. Others see it as an indictment of racism. The debate continues because the book provokes it.