In the 19th century, European and North American missionaries spanned the world, bringing the light of the gospel into what they thought were the dark corners of heathendom. In many regions, though, the natives did not react as the newcomers expected. Their response was not “Thank you for bringing us this startling new message” but rather “Welcome back.” What the missionaries had not realized was that Christianization need not be a definitive, once-and-for-all act, a one-way process. Religions come and go. White Christians were treading where African and Asian believers had been before and where they had left deep marks in local cultures. Their ghosts still walked.