From the moment Carrie Cairncross enters Port Vernon's strange August fog, she wonders whether curious events are merely coincidences or indications of a deeper mystery.

When Carrie and her friends Booj and Greg discover a magical shadow that takes them wherever they wish to be, they anticipate a week full of adventurous fun. However, they are totally unprepared to find themselves in the middle of a plot to steal the earth's animals, unpredictable journeys to past and future worlds, time and space warps emanating from their town, a ruthless search for eternal youth, and sinister forces...