I'll Come to Thee by Moonlight — Florence Byham Weinberg

A grisly murder by beheading near the Jesuit mission of Guevavi in the Sonora Desert in 1761. Whodunnit? Indians? Settlers? Fr. Ignaz Pfefferkorn, S.J., although suffering from malaria, undertakes an investigation. Ignaz has survived so far thanks to the charismatic maakai (medicine man) Gevho and his half-Indian, half-Irish assistant, Patricia O'Meara. Patricia, torn between two cultures, loves both Gevho and the priest, and must choose which path to follow. Ignaz sets about solving the murder, enlarging the mission, and converting Gevho and his tribe. He applies Jesuit principles, accepting any aspect of native religion in harmony with Christianity. His superiors admonish him for suspected heresy and for being too involved with Gevho, but Ignaz persists in his endeavors. After placing himself in mortal danger several times, the priest succeeds in solving the murder, but must face discipline by his superiors for disobedience.