Folklorist Keira Sullivan, trapped in a collapsed ruin while in Ireland researching the legend of an ancient Celtic stone angel, is saved by Simon Cahill, an agent of Fast Rescue, a rapid-response search-and-rescue organization, and together they explore the link between Keira's close call and Cahill's investigation of a serial killer who seems to operating on both sides of the Atlantic.

It was meant to be an adventure, a night alone on a remote Irish island. Archaeologist Sophie Malone never expected to find Celtic treasure or to end up in a fight for her life in a dark, desolate cave. Now, a year later, she's convinced answers to the mysteries of that night lie in Boston. Who has the priceless gold artifacts that disappeared from the cave...and who is responsible for the whispers she heard in the dark? Nearly killed in an explosion...