Based on the famous novel by Alan Furst, the series was adapted by Emmy Award-winning screenwriters Dick Clement and Ian LaFrenais. In 1914, the whole of Europe was shrouded in the shadow of Hitler's Nazi regime. Colonel Mercier (David Tennant), who won a high medal in World War I, was stationed in Poland as a military attaché. The colonel obtained intelligence from his German informant Edvard that Hitler's Nazis were secretly planning a plan to invade Poland. Mercier was almost killed while on duty and escaped with great difficulty. French bureaucrat Jourdain had a deep prejudice against Mercier, fearing that Mercier's actions would further intensify the diplomatic situation. Parisian lawyer Anna (Janet Montgomery) and Mercier also fell in love with each other during this dangerous period. But Anna also has an inseparable relationship with her husband Maxim, who is a political reporter. The entangled relationship between the three people became more and more tense as the war began...