While Henry Sachs lies in a hospital bed, dying from a mysterious illness, Perry must uncover the secrets of his father's past to try to save his life. Perry believes that Henry's condition stems from a time when he worked to investigate a secret underground base not built by the U.S. After a year of research yielded almost no information, a drastic decision was made: To prevent the base's unknown builders from ever returning a dam was built, flooding the area. What holds Henry Sachs in its grip? Can Perry face his toughest excavation yet-and find out before it's too late?