In the autumn of 1901, Charles Carruthers [Michael York]—a refined junior official in the British Foreign Office—is invited on a yachting and duck-shooting holiday by his old university associate, Arthur Davies [Simon MacCorkindale]. As they sail toward Germany’s northern coast to join the yacht Dulcibella, Davies drops a secret: the trip carries a hidden purpose beyond sport and sea air. On board, Davies reveals that he has already become entangled with the tale of a retired German sailor, Dollmann [Alan Badel], who travels with his wife, Frau Dollmann [Olga Lowe], and their daughter Clara [Jenny Agutter], a girl who has drawn Davies’ protective attention. Davies’ insinuations point to something larger than recreation: he believes the Imperial German Navy is quietly testing dangerous capabilities in the Frisian Islands, a move meant to threaten Britain’s security and to force the Royal Navy into a costly strategic misstep.
Carruthers, with his fluency in German and his Whitehall connections, becomes an unexpected ally in Davies’ high-stakes probe. The voyage becomes a tense game of shadows as circling German naval officers issue cryptic warnings, and the crew sails among the inlets and shifting sands of the Frisian archipelago. The pair uncover evidence that a hidden German naval base in the islands is rehearsing a seaborne crossing of the North Sea, with the explicit aim of landing a German army on British soil. The critical figure behind the scheme is Dollmann, revealed as Lieutenant Thomas—a disgruntled former Royal Navy officer aiding the German effort with intimate knowledge of Britain’s coast and defenses.
Tensions erupt when the two Englishmen and their new information confront the danger head-on. After sabotaging one rehearsal, they make a desperate escape to the Netherlands aboard two roped-together yachts, bringing with them Dollmann and his family as prisoners. Davies, pressed by the need to secure medical care for Dollmann’s wounds, makes a difficult choice: he abandons Dollmann and Frau Dollmann in the Dulcibella so that Clara can accompany Davies and Carruthers back to Britain aboard the Medusa, carrying papers that detail the German plans in full. The pursuit closes in as German authorities close ranks, and Dollmann and his wife meet a brutal fate when the Dulcibella is rammed and destroyed, the order coming from the highest echelons of power, led by Kaiser Wilhelm II [Wolf Kahler].
With the wounded threat behind them, the yacht trio—Carruthers, Davies, and Clara—set a course toward the Netherlands. The narrative closes on Carruthers’ voice, reflecting on how their careful transmission of information will steer Britain’s maritime defenses toward a more wary and strategic posture, potentially averting a broader war through tactical deterrence. The voyage is as much about trust, loyalty, and the price of secrecy as it is about military reconnaissance, leaving a lasting impression of how single moments at sea can reshape a nation’s approach to peace and security.
