Sor Mar a de Agreda (1602-65) was a Spanish nun and visionary who is best known as the author of the widely read biography of the Virgin Mary, The Mystical City of God, and as the missionary who "bilocated" to the American Southwest, reportedly appearing to Indians there without ever leaving Spain. Her role as advisor to King Philip IV contributed further to her legend. Clark Colahan now offers the first major study of Sor Mar a's writings,...