Mary Withall spent thirty years in Secondary and Further Education, lecturing in Natural Sciences, Nutrition and Health subjects before retiring to the Island of Easdale in Argyll in 1998. She became the archivist to the Easdale Island Museum in 1989 and has been associated with the museum ever since. She is a founder member and trustee of the Slate Islands Heritage Trust which was formed in March 2000.
In 1995, Mary published the first of her trilogy of historical novels based on the history of the Slate Islands. Since then she has published five further novels all of which are available in paperback.