London 1940. With the nation bowed down by war, the government turns to propaganda films to boost morale at home. Realising their films could use ‘a woman’s touch’, the ministry hires Catrin Cole (Gemma Arterton) as a scriptwriter. Catrin’s natural flair quickly gets her noticed by cynical, witty lead scriptwriter Buckley (Sam Claflin). Catrin and Buckley set out to make an epic feature film based on the Dunkirk rescue starring the gloriously vain, former matinée idol Ambrose Hilliard (Bill Nighy).