In this heart-stopping thriller by acclaimed author Mark Sullivan, marine biologist and cave researcher Whitney Burke vows that she will never set foot underground again. Still traumatized by the tragic loss of her assistant on her last expedition, Whitney can only watch from a distance when her husband and daughter agree to join a NASA-sponsored caving trip. When the expedition is seized by a band of criminals—effectively holding her family hostage—Whitney must surmount her all-consuming fear and put everything on the line for her family. Battling her own terror and the paralyzing elements of the subterranean atmosphere will take all the knowledge and strength Whitney has in this high-stakes tale of adventure. “Expertly crafted, [LABYRINTH] is one of the most exciting yarns of this millennium. Brilliantly told and realized. A great read.”— Publishers Weekly (starred review)