Amid World War II’s chaos, a hidden battle rages — a war of espionage, deception, and codebreaking. At Bletchley Park, Alan Turing and his team race to crack Germany's "unbreakable" Enigma Code in a bid to thwart Nazi plans and save Britain from invasion. But as the codes evolve, daring missions and deadly risks intensify…

This episode features interviews with (in order of appearance):

• Dan Snow, historian and broadcaster
• Robert Citino, senior historian, National WWII Museum
• David O’Keefe, professor, Marianopolis College
• Nicholas Reynolds, historian and former CIA officer
• David Abrutat, Official Historian, GCHQ
• Sir Dermot Turing, writer and speaker
• Matthew Hefler, intelligence historian, King’s College London
• Tessa Dunlop, historian and author
• Guy Walters, historian and author
• Katrin Paehler, professor, Illinois State University
• Robert Hutchinson, intelligence historian