Although striving to make an honest living running a small yacht for charter, Edward Furse dreams of a better life for himself and his son Jimmy, and when a mysterious Dutch passenger dies on the voyage back to Holland, Furse finds that fate may have placed him on the path to good fortune. Checking through his deceased passenger's possessions, he finds papers and charts which suggest treasure long buried and forgotten. Gems ready for the taking, if only he can decipher where along the Haringvliet to find the House of the Seven Flies.

With a dead passenger aboard, Furse's arrival in Holland is met with some suspicion and soon it is not only Inspector Molenaar who is keeping the English sailor under his watchful eye, but also Rohner, a man as well-known for his wealth as his dishonest ways in acquiring it. With dangerous competition, Furse starts to hunt for clues that can lead him to the Seven Flies and the jewels that will secure a prosperous future. However, the journey towards fortune is less than simple and Furse has to grapple with both his own conscience and a beautiful woman, whom he knows deserves more than a smuggler and a thief. . .