Sonora, 1761-62: Father Ygnacio Pfefferkorn, SJ, suffering from acute malaria, is transferred to a new mission, Guevavi in present-day Arizona. Healed by a Pima medicine man: Jevho, and his half-Pima, half-Irish nurse-assistant Patricia O'Meara, he becomes obsessed with converting Jevho to Christianity. A grisly murder is discovered near the mission, and Ygnacio sets about solving the crime, fearing his mission Indians will be blamed. Suspects abound in the small Irish ranching community and among Jevho's people. Patricia, in love with both the priest and Jevho, must choose between cultures, native or European.