The first portrait of spiritual luminary Thomas Keating's remarkable evolution, in the last decades of his life, into a fully realized modern-day Christian mystic. In the first four decades of his life as a Trappist monk, Thomas Keating created a comprehensive, unified psychospiritual pathway leading from healing to holiness and from contemporary psychological wellness to classic mystical sanctity and beatitude. As one of the key innovators of the meditative practice of Centering Prayer, he fashioned a powerful on-ramp to the Christian contemplative tradition. Yet, as beloved author and Keating disciple Cynthia Bourgeault shows, that was not the end of Keating's story--his evolution as a spiritual thinker and mystic continued in ways few have explored in depth. In this unique blend of biography, personal experience, and close reading of his late works, Bourgeault illuminates Keating's remarkable spiritual development from the late 1980s until his death in 2018. She explores: Keating's increasing engagement with nondual spiritual practice His contributions to interspiritual dialogue The evolution of his early teaching on the movement from "false self" to "true self," to that from "true self" to "no self" His final "dark night of the spirit" and passage through death New evidence that he never left Christianity but carried it with him to new places These profound final stages of Keating's spiritual journey demonstrate how readers might find their own way as modern mystics, fundamentally at home and at peace in the universe.