In August 1939, the Honorable Duncan Morant, only son and heir of the second Lord Eversham, is enjoying life as a man-about-town, and skippering his racing schooner Kristin. But he is also a sub-lieutenant in the Royal Naval Volunteer Reserve, and as the war clouds gather he is called up. Because of his experience in small boats, and his knowledge of navigating the waters of the English Channel, Morant is given command of one of the new, small, fast motor-torpedo-boats. This is a disappointment, both because he had hoped for a place on a battleship, and because no one in the Navy seems to know exactly what these boats are to be used for; the English Channel is very much a British preserve. However, as the War takes a disastrous turn in 1940 it becomes a battleground and Duncan and his crew, in their plywood hull, find themselves in the thick of several hazardous operations....