1915. German guns are on their way to Ireland. The British government faces its worst nightmare; insurrection at home while it struggles with bloody stalemate on the Western Front. A British spy, Sebastian Wolff of the new Secret Service Bureau, is given the task of hunting down its enemies: one a traitor reviled by the society that honoured him as a national hero; the other a German-American doctor who, instead of healing the sick, is developing a terrifying new weapon that he will use in the country of his birth. Wolff's mission will take him undercover into the corridors of power in Berlin, then across the Atlantic in a race against time to prevent the destruction of the ships and supplies Britain so desperately needs to stave off defeat.