The great wheel - Ian R. Macleod

Although Father John has lost his faith, he gamely administers medicine and prayers to the people of a Borderer town in what was once northern Africa. He wonders why so many of them are dying of bludrut-myeloid leukemia-and suspects that the koiyl leaf, chewed as an opiate, may be the reason. Investigating, the priest from Europe encouneters politics and poverty, finds the love of a Borderer woman, succumbs to the power of a drug, questions a first world grown too perfect in its biotechnology-and at last makes his peace with the pain of personal loss.