It is October 1918 and Germany is suing for peace. All U-boats have been ordered home from patrol. Among them is U81, commanded by Otto von Mettendorff: young, dynamic, and infatuated with a girl who works near Wilhelmshaven, the port U81 is now returning to. Unfortunately, U81 is holed by a destroyer on its way home.

Meanwhile in London, Anne Laurie, a young war widow employed in the Intelligence Division of the Royal Navy, learns of Otto's death. It jolts memories of a pre-war weekend in Berlin in the summer of 1913; the genesis of a compulsive story of two magnetic people torn apart by global conflict…