With tensions in Prague rising at the height of World War II, Isaac Wolf is forced to leave home with nothing more than a small backpack and a pendant in the shape of an eternity knot. His parents believe the pendant will keep him safe--if he can discover what it really means. This clue leads him to Rookskill Castle, home of the Special Alternative Intelligence Unit where gifted children can learn to harness their powers to support the Allies' cause....

In 1940, during the Blitz, Katherine, Robbie and Amelie Bateson are sent north to a private school in Rookskill Castle in Scotland, a brooding place, haunted by dark magic from the past--but when some of their classmates disappear Katherine has to find out if the cause is hidden in the past or very much in the present.

In 1904, sixteen-year-old Maggie Bennet's father tears her away from their elegant Newport, Rhode Island, home on an ill-advised excursion to Yellowstone in Montana to look for her mother, who has disappeared and is presumed dead, and once there, she finds herself drawn to the son of a park geologist, and to the wild beauty of Yellowstone itself.