From the start it is obvious that something is going on behind the placid facade of the Frisian islands and towns. The protagonists gather hints, follow clues and form various hypotheses. There are many red herrings – for example, for much of the book, their suspicions centre on Memmert. However, though that island provides a convenient cover for the German plotters to meet and talk, what is actually going on there is a genuine salvage operation seeking a cargo of gold from a French ship sunk during the Napoleonic Wars. The actual German design, revealed only at the end – a full-fledged, meticulous plan for the invasion of England – is in fact unfolding among very mundane and prosaic small Frisian towns and harbours.