Supporting Roles is a fictional elaboration of the lives of five figures in the New Testament whose continued lives are not documented in that source. However, in the legends of Cyprus and Provence there are stories which relate as to the history of Lazarus, Marta and Mary of Magdala.
The author was intrigued by the number of churches dedicated to La Madalene and St. Lazaire in Provence during his residence there and searched for an origin to these tales. There is a section of Provence called, locally, le desert, and Mary of Magdala is supposed to have retired there until her death. Hence the churches dedicated to her. Lazarus (correctly Eliazer) is, by tradition, the first Bishop of Aix-en-Provence. The fictional extrapolation of their lives stems from these legends.