At age forty, Dutton had a spiritual rediscovery that led to his becoming a Catholic. Soon thereafter he entered the Trappist monastery of Our Lady of Gethsemani in Kentucky, where he spent two years.
After hearing of the work that Blessed (soon to be Saint) Damien De Veuster was doing among the lepers of Molokai in the Hawaiian Islands, Dutton made his way on foot to San Francisco, and from there he got a ship for Hawaii. It was his intent to work among the lepers, and by so doing atone for the sins of his past life. In June 1886, he arrived on Kalauppa, Molokai Island, where he met Father Damien. He stayed there for forty-five years. Dutton served as a lay brother, assuming the name of Joseph. When Father Damien died in 1889, Brother Joseph assumed the duties of administrative assistant of the colony. He worked among the lepers, nursing them and continuously striving to improve their living conditions. Among his other accomplishments, he founded the Baldwin Home, a residence for leper men and boys.
In his later years, Brother Joseph was honored by the Hawaiian government. As illness and old age took their toll, he found it necessary to go to a hospital in Honolulu where he died at age 88. At the time of his death, he was praised as “an incentive to virtue… a man who for many years had preached the loving charity of Our Lord Jesus Christ.”