The Santander family is on its way to the town of Grand Prospect to take part in a Great Race to map a route through the mountains between there and the town of Coalhaven. The impoverished family want to win the lavish prize and fund a search for their missing explorer father. However, a mishap at a train station sees their mother stranded while the children are carried onwards. With the race due to begin the next morning and twenty-eight days to reach the finish, they bravely decide to start the race by themselves.
Joe is the trailblazer, taught by his father to strike out ahead to find safe and suitable routes through the wilderness. Sal is the mathematician, calculating heights and distances using trigonometry and their trusty altimeter. Humphrey is the baby of the group and Carrot is the parrot. They are joined by Beckett, who thinks their route will see a train station bring prosperity to his village one day and who may be able to keep them alive by rationing their meager supply of food. But it is their silent sister Francie and her amazing map-drawing talent that they hope will win them the prize in the face of stiff competition from the other teams, who are not above cheating and stealing… and even kidnapping.
A thrilling and thoroughly enjoyable adventure full of setbacks and dangers and family squabbling, but also fun and laughter and the thrill of exploration and storytelling around campfires under the open stars. The family are immediately likable even as the odds are stacked against them, but their skills and their loyalty and perseverance help them win through time and again.