The future repeats the past in slightly new form. We're in a new Cold War now, so we might as well study the old. It makes sense to explore the Cambridge Five, Kim Philby, Ronald Pelton, John Walker, and probably Benedict Arnold. This series, driven by the immensely powerfuly Jodie Whittaker, explores the search for a double agent in an organization utterly unprepared for the wave of betrayals that happened after the 1960s.