"Sal, Joe, Francie and Humphrey Santander are mapmakers looking for their father, a famous explorer who disappeared on his last expedition. Their search takes them to Cruxcia, where the people are fighting to protect their land from the all-powerful Grania Trading Company. The Santanders mapping skills may be the missing piece in the Cruxcian race to save the ancient valley - and the key to reuniting their family"--Back cover.