Publisher's Synopsis
Carruthers, a minor official in the Foreign Office, is contacted by an acquaintance, Davies, asking him to join in a yachting holiday in the Baltic Sea. Carruthers agrees, as his other plans for a holiday have fallen through, and because of a heartbreak due to a woman he courted becoming engaged to another man.He arrives to find that Davies has a small sailing boat (the vessel is named Dulcibella, a reference to Childers's own sister of that name), not the comfortable crewed yacht that he expected. However Carruthers agrees to go on the trip and joins Davies in Flensburg on the Baltic, whence they head for the Frisian Islands, off the coast of Germany. Carruthers has to learn quickly how to sail the small boat.Davies gradually reveals that he suspects that the Germans are undertaking something sinister in the German Frisian islands. This is based on his belief that he was nearly wrecked by a German yacht luring him into a shoal in rough weather during a previous trip. The yacht was owned and captained by a mysterious German entrepreneur called Dollmann, whom Davies suspects of being in fact an expatriate Englishman posing as a German. The situation was further complicated by Davies having fallen deeply in love with Dollmann's daughter, Klara - who, Davies is sure, is not involved in whatever nefarious scheme her father is engaged upon. In any case, Davies is suspicious about what would motivate Dollmann to try to kill him, and believed that it is some scheme involving the German Imperial government. Having failed to interest anyone in the British government in the incident, Davies feels it is his patriotic duty to investigate further on his own - hence the invitation to Carruthers.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 Bruning - 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.Taking advantage of a thick fog, Davies navigates them covertly through the complicated sandbanks in a small boat to investigate the Memmert site. Carruthers investigates the island. He overhears von Bruning and Dollmann discussing something more than treasure hunting, including cryptic references to "Chatham", "Seven" and "the tide serving", and hear of a rendezvous at the Frisian railway station, several days ahead. The pair return through the fog to the Dulcibella, moored at the island of Norderney. There, they find Dollmann and von Bruning have beaten them and are seemingly suspicious. However, getting in the fog from Norderney to Memmert and back is a nearly impossible feat, which only Davies' superb seamanship could have achieved, and the Germans do not seriously suspect them of having done that.Von Bruning invites them to Dollmann's villa for a dinner, where he attempts to subtly cross-examine them to find out if they are British spies. Carruthers plays a dangerous game, admitting they are curious. But he convinces von Bruning that he believes the cover story about treasure and merely wants to see the imaginary "wreck". The party also serves to show that the Germans do not fully trust the renegade Englishman Dollmann and that there is some rift between them which might be widened.
