In 1558, while exiled by Queen Mary Tudor to a remote castle known as Perilous Gard, young Kate Sutton becomes involved in a series of mysterious events that lead her to an underground world peopled by Fairy Folk—whose customs are even older than the Druids’ and include human sacrifice.

As Kate navigates this enchanted realm, she uncovers secrets that intertwine with ancient myths and legends. Her journey is one of intrigue, courage, and discovery, as she confronts the magical and the unknown.