In their most ambitious adventure yet, our two heroes are asked if they could extend their mini railway to the village of Oaksted. It is five miles across the fields and will bring children to school, saving fuel and pollution. Of course they would love to build the new line, but how can they possibly afford to pay for it?
There is science and engineering in the story but, if the reader wants to go deeper, there is more in the technical pages at the ends of chapters. As an extra dimension in this story, Peter starts a company and becomes an entrepreneur. During breaks in construction work, Grandpa tells some more of his historic stories about the old railways.