In the first episode of Dig WW2, historian Dan Snow investigates the history of the Second World War in Northern Ireland, participating in archaeological digs and dives of military sites across the country. He discovers the gripping story of the Northern Irish pilot who became the most successful U-boat hunter of all time. He also dives to the wreck of the famed U-155 and reveals the essential role that Belfast's Harland and Wolff had in developing the famous Churchill Tank, fundamental to the march of the North Irish Horse to capture Rome. Meanwhile, in Donegal, a major excavation reveals the 70-year-old Spitfire flown by US pilot Bud Wolfe, who was forced to bail out just minutes after leaving RAF Eglington, now City of Derry Airport.

In our second episode of Dig WW2, Dan Snow heads out to sea to hear the story of the Empire Heritage, a cargo ship filled with Sherman Tanks sunk off Malin Head during the Battle of the Atlantic in 1944. Staying on the water, he visits an RAF Flying Boat Base on Lough Erne, where he gets to fly in an original WW2 Catalina, an aircraft built for hunting U-boats. Dan also gets to hear some of the stories which bring a personal aspect to his discoveries, visiting a group of experts intent on discovering the unknown identities of bodies of Second World War soldiers and finally bringing closure to their families all these years later.

In our third episode of Dig WW2, historian Dan Snow travels to Lough Foyle to dive on a Flying Fortress that never made it on a bombing raid. Unearthing stories of the crew, we hear how they miraculously survived the crash helped by a local woman and her sailboat. He then heads to the shores of Lough Neagh where, at RAF Cluntoe, pilots and crew were trained for flying missions all over Europe. Finally, he reveals the climactic end of the Battle of the Atlantic on the River Foyle docks, where the German navy surrendered their U-boat fleet and from where they set out to be sunk off Malin Head. Dan returns to this U-boat graveyard to dive on one very special submarine, which could have spelled victory over Germany, but arrived just too late.