On a dark night in the Danish harbor of Drag¯r, Ulf is handed a log-book by a lone sailor who then disappears. The bizarre events recorded in the log lead Ulf and his friend Torben to make a dangerous winter crossing of the North Sea to Scotland in the 31-foot yacht Rustica. As they are passing through the Caledonian Canal, a lock-gate bursts open and nearly puts an end to their boat and their lives. Is this an unlucky accident, or attempted murder? Is the black fishing boat, F154, following them, or is that a coincidence too? The answers they find will draw them into a deadly duel with arms smugglers and followers of a Druidic cult across some of the most dangerous sailing areas in the world.

First published in Sweden, Bjšrn Larsson's thriller became a bestseller in Europe and has been compared by critics to Erskine Childers' The Riddle of the Sands. Like Childers, Larsson combines a mastery of sailing description with an intriguing plot that unfolds to a macabre denouement on an ancient Celtic site.