1940 as World War II rages on, an Anglo-Irish spy uncovers a secret pen of German U-Boats. Meanwhile Nazi agents multiply in Ireland & a parachute drop is imminent somewhere. Operation Code Name EMERALD is put into effect! Four decades later his son a bestselling author & historian, is doing research for his latest book. When he receives a mysterious letter. Was his father on to something? Were the Germans really preparing to invade Ireland? Both men are being hunted by powerful foes who want the truth to remain hidden.