What is the theme in The Viceroy of Ouidah by Bruce Chatwin?

The price of sin is a major theme in this story. This is not a religious novel and yet religious practices play a prominent role in it. Many of its characters are influenced by religion, although few, if any, follow its tenets in ways that reflect proudly on their humanity. It appears that the author's intent is to suggest that those who choose to do evil will pay, even if only in the degradation of their own decency. His theme is not overtly religious, however, because he gives no indication that a deity is exacting punishment on anyone.