Carruthers and Davies spend some time exploring the shallow tidal waters of the Frisian Islands, moving closer to the mysterious site where there is a rumoured secret treasure recovery project in progress on the island of Memmert. The two men discover that Dollmann is involved in the recovery project. Carruthers and Davies try to approach Memmert. They are warned away by a German Navy patrol boat, the "Blitz", and its commander von Brüning - who is friendly and affable, but still makes a veiled warning. This makes them all the more sure that there is something more than a treasure dig on the island. And meanwhile, they discover that, not only is Dollmann indeed an Englishman, he had been an officer in the Royal Navy - evidently having had to leave Britain in hurry and take up a new life as a German.