Summer1939.TranslatorHarry(JonahHauer-King)isworkingattheBritishEmbassyinWarsaw,fallinginlovewithPolishwaitressKasia(ZofiaWichłacz).WhenGermantanksrollintoPolandandBritaindeclareswaronGermany,HarryandKasiaarefacedwithterriblechoices.ccc
Withherlifeingravedanger,theonlywayforKasiatobesafeistoescape.CanHarryhelpher-andifhedoes,howwillheeverexplainhimselftofactoryworkerandsingerLoisBennett(JuliaBrown),thegirlheleftbehindinManchester?
AstheNazithreatspreadsacrossEurope,Kasiamustchoosebetweenloveandfightingforhercountry,Harrymustfindhisplaceintheworld,andLoisseizesnewopportunitiesthewarthrowsup.TheconflictoverturnseverythingforHarry'ssnobbishmotherRobina(LesleyManville)andforDouglas(SeanBean),Lois'pacifistfather,andherfirecrackeryoungerbrotherTom(EwanMitchell),whojoinsthenavyandfindshimselfunderfireinoneofthefirstmajorbattlesofthewar.
InBerlin,outspokenAmericanjournalistNancy(HelenHunt)risksherlifetryingtohelpherneighbourstheRosslersfromtheattentionsoftherulingNaziregime,whileinParisNancy'snephew,medicWebster(BrianJ.Smith)refusestoleavethecityandthemanheloves.
Thisisaseriesthattakesusacrossthefirstyearofthewar,fromordinarylifeinManchestertothebeachesofDunkirk,gettingrightundertheskinandintotheheartsandmindsofthoselivingtheirlivesduringthisextraordinarytimeastheygrapplewiththeunthinkable:aworldinflames.