It is 1940. France has fallen, and only a narrow strip of sea lies between Great Britain and invasion. The war could go either way, and everyone must do their bit. Copywriter Catrin Cole is drafted into the Ministry of Information to help “write women” into propaganda films—something the men aren’t very good at.

She is quickly seconded to the Ministry’s latest endeavor: a heartwarming tale of plucky sisters who help rescue British soldiers from the beaches of Dunkirk. It’s all completely fabricated, of course, but what does that matter when the nation’s morale is at stake? Since call-up has stripped the industry of its brightest and best, it is the callow, the jaded, and the utterly unsuitable who make up the numbers. In a nation under siege, they must all swallow their mutual distaste, ill will, and mistrust to unite for the common good, for King and Country, and—in one case—for better or worse. . . .