Four children, quadruplets, have just returned from their grandfather's funeral. Using special gifts and a book that were created by Grandfather Adam, the children are magically transported to the Lands of Nosisis. Upon arrival, placed at the foot of a great mountain, the children are separated, taken to the four corners of this fantastical realm. Lost in an unknown land, John, Mary, Thomas, and Martha struggle to reunite. John must overcome the desert wastelands of Pythagore and the monstrous Marage. Mary encounters the underwater realm of Lunariamar and the sea-dwelling Undinar. Thomas, forced into the army, attempts to escape the warring lands of Corpusolo. Meanwhile, Martha crosses the Jungle of Urg, assisted by the tribal Mawisis people. Aided by their special gifts, and by new friends and mythic creatures they meet along the way, the four make their way back toward the mountain, and their lost grandfather's home.