Siobhan was that shy maid who was terrified of the Fey and magic. That's who Corrine knew her as when she was the narrator. As it turns out, she discovers a braver part of herself when she freely chooses to step into a Fey (fairy) rath (realm) to find a rathstone (stones of incredible power, capable of opening and closing raths and enhancing magical power) open Hallowmere (a pool of magic where the Fey once came to reincarnate themselves).

Siobhan finds herself in twelth century Scotland, before the Unhallowed (Fey that drink the blood of mortals instead of going to Hallowmere) came into being. She is reliving the very event that in the future, was the reason she stepped into a rath in the first place.
But this time, she has a chance to change history. Fey history. If Siobhan can prevent the Unhallowed from ever coming into being, and return to the furture, the terrible battle that is taking place there will instantly disappear-and none of them will need to go on their dangerous missions to retrieve the rathstones.