Fleet buildups in England and Germany cast the shadow of the First World War. Why do the two young Englishmen, Davis and Carruthers, go on a sailing trip through the sailing trip through the North German Wadden Sea? Why are they putting themselves and their boat in danger?

On Norderney Davies gets to know the rich merchant Dollmann, supposedly a Swede. Davies lets himself be Davies is guided through the Wadden Sea by Dollmann's yacht - and almost dies. An attempted murder? Daives and Carruthers get caught in a whirlpool of mysterious of mysterious events. Is Dollman making common cause with the Germans against England? Davies falls in love with Dollman's seductive daughter Clara. Is Dollman just using her as a tool - against whom? And what role does role does Frigate Captain von Brüning play in the plot?