In a wretched third world of the future, a young priest from England pursues the mystery of a disease. Although Father John has lost his faith, he does his best to administer prayers and medicine to the people of a Borderer town in what long ago was northern Africa. He wonders why so many in the Endless City are dying of bludrut - myeloid leukemia - and begins to suspect that the reason is the koiyl leaf, which the people chew as an opiate. Investigating, John encounters poverty, politics. He travels to a far valley of radioactive death, his guide a witch-woman. And as he questions a Europe grown too perfect and falls in love with a Borderer, he is visited, constantly, disturbingly, by childhood memories of harvest fairs at Hemhill and a wonderful older brother.