Mr Fortune's Maggot

From Amazon.com:

After a decade in one South Seas mission, a London bank-clerk-turned-minister sets his heart on serving a remote volcanic island. Fanua contains neither cannibals nor Christians, but its citizens, his superior warns, are like children—immoral children. Still, Mr. Timothy Fortune lights out for Fanua. Yet after three years, he has made only one convert, and his devotion to the boy may prove more sensual than sacred. Mr. Fortune’s Maggot, Sylvia Townsend Warner’s second novel, is lyrical, droll, and deeply affecting, and her missionary captivated his creator as much as he did her readers.