Growing desperate in 1943, Hitler hatches a diabolical weapon: a bank of "superguns" housed in a massive underground complex in Nazi-occupied northern France. Together the guns would be able to pump 600 high explosive shells 100 miles into downtown London every hour. This weapon could spell doom for the allies. But how can such a massive gun possibly work? Join NOVA as engineers, archaeologists and WWII historians investigate this fearsome weapon. And discover the two audacious missions designed to destroy the seemingly impregnable supergun complex, one of which is led by Joseph Kennedy, Jr.