Mackay was born in
Edinburgh in 1959. Mackay left drama teaching to study creative writing at the
University of Sussex where she completed a master's degree in 2004. She was appointed as a writer in residence by the
Scottish Arts Council to reside in
Caithness in northern Scotland. She was there for five years and she wrote poetry about the landscape and her first book.
Magnus Fin and the Ocean Quest, won the Kelpies Prize in 2009. The next book,
Magnus Fin and the Selkie Secret, continued the story. Mackay had a short residence in Helsinki in 2012. In 2013 she won the
Scottish Children's Book Award for her book
The Accidental Time Traveller. She received £3,000. She was congratulated by
The Guardian and the paper published a list of the top ten books she had read that were set "on the ocean". Her first choice was
Kidnapped. In 2022 she was one of ten writers who created work to support a bid to gain
UNESCO World Heritage Status for the
Flow Country. The Flow Country of Caithness and Sutherland and its blanket bog system gained World Heritage Status in 2024. Her thirteenth book was her first for adults and it was published in 2025. The story is set in a fictional village by the sea in Caithness and it concerns a lonely fisherman and his encounter with what he believes to be a
selkie. ==Family==