A fresh and exciting mapmaking adventure. Sal, Joe, Francie and Humphrey misplace their famous mapmaker mother as they begin the Great Race to map a rail route through an uncharted wilderness. Their father didn't return from his last expedition and now their money is gone. This race is their last chance.

They have twenty-eight days to find and map the best route. There'll be bears, bees, bats, river crossings, cliff falls, impossible weather-but worst of all, they're racing five teams of adults who do not play by the rules.