This article presents materials about Sofia Nikolaevna Sleptsova, a spiritual writer who corresponded with prominent hierarchs of the Russian Orthodox Church: St. Theophan the Recluse, Archbishops Leonid (Krasnopevkov) and Nikon (Rozhdestvensky). The literary pseudonym “Syrophoenician,” suggested by Bishop Theophan when publishing her poems in “Athon Leaflets” and the journal “Soul- Beneficial Reading,” concealed the author’s name for many years. It became possible to establish the authorship of the works by S. N. Sleptsova through an analysis of surviving letters from St. Theophan. Individual episodes of Sleptsova’s biographical background have been reconstructed from previously unpublished archival documents, including those from the Kugushev family archive, close relatives of Sleptsova. A true discovery was a description in the unpublished 1874 diary of Bishop Leonid (Krasnopevkov) of his meeting with Sleptsova. The recollections presented in this article paint a picture of the life of a gifted woman, a suffering mother, who remained faithful to spiritual and moral traditions and religious values.