Sal, Joe, Francie and Humphrey misplace their mother as they begin the Great Race to map a rail route through an uncharted wilderness. Their money is gone and their father didn’t come back from his last adventure. This race is their last chance.

They have twenty-eight days to find and map the best route through the mountains. There are bears, bees, bats, river crossings, cliff falls, impossible weather—but worst of all, they’re racing four teams of adults who aren’t playing by the rules.