This is the first biography of Sister Mary Michael, who died on February 25, 1934. The author was a pioneer of historiography and spirituality of the Arnoldus Family – Father Hermann Fischer. In the introduction to the book he writes the following: “After teaching in the diaspora for ten years, Adolfine Tönnies joined the newly-founded Congregation of the Steyl Missionary Sisters. Five years later its Founder, Fr. Arnold Janssen, appointed a group of Sisters for the ministry of perpetual adoration, thus laying the foundation for the new Congregation, Servants of the Holy Spirit of Perpetual Adoration. Adolfine Tönnies who, by that time, bore the religious name Sister Michaele, was one of the first members in the new Congregation. According to the plan of Providence, she was called to be its first superior. For nearly four decades, she was so involved in its inner and outer construction that she can rightly be called its co-foundress. In many respects, her story is the history of this Congregation, and the spirit of this Congregation is essentially a mirror of her own spirit.”