It s a boarding school in the early 1930s that Cissie, Mary and Peg first meet. A deep and lasting friendship is forged between them, strengthened by their association with Glenallen, the mysterious and forbidding home of the wealthy Fitzallen family, overlooked by the brooding mountain, Knockshee.

Taking us on an compelling journey between Ireland and England, now under the shadow of war, Glenallen traces the intertwined lives of these three women - all caught in a chilling web of powerful emotions, family hatreds and the intangible presence of a deep and ancient force ...