Mark and James set off for a fortnight's camping holiday on their uncle's farm, in the country, together with their mischief-making Alsatian - Archer. On the farm they join up with their cousin Rebecca and together they find MUCH more than a simple holiday when their trip coincides with a series of burglaries in the tiny village of Mainswell. Why are two men meeting beneath the campsite in the dead of night? What is going on in the disused windmill? And who is Harry? The anwer to these questions and the strange happenings that make up the Mystery At Mainswell all await you as you join Archer, the boys and Rebecca.