Sitting in his flat on Île Saint-Louis overlooking the Seine River in Paris in 1928, literary agent Bill Lawrence gets a letter from American foreign correspondent Kurt Eckhart in Berlin. Bill knew Kurt during World War I when both were infantry officers in the 3rd Division of the American Expeditionary Force that fought across France in 1918. Kurt is writing the great American war novel. Can Bill get it published? Bill writes back "Yes." Later, the two meet at a café in Paris to review the novel. The novel is about a brave war, the army's drive across France, and a failed peace-the aftermath in Germany in 1919 and 1920 when the peace was lost. Kurt briefly explains the plot: an American officer meets a German nurse in the winter of 1919 in Koblenz; the nurse gets pregnant, the officer resigns from the army and the couple goes to Berlin where the nurse is later hit by bullets from a street riot in a failed putsch in early 1920. She dies in hospital for lack of supplies stemming from the Allied blockade-the story dramatizing the failed peace.

Just then freelancer Kate Lundberg wanders into the café and Bill invites her to join the project as copy editor. For Saturday night dinner, Bill sets up Kurt with Madeleine, a French publishing assistant at an off-color publishing house. Bill invites Kate to go along. The two couples finish with dancing at Bricktop's, a Montmartre jazz cabaret. Kurt invites Bill and Kate to Berlin for even wilder nightlife. In Berlin, Kurt explains that while in the army he worked with economist John Maynard Keynes in 1919 to get needed food into starving Germany, a positive effort in the overall failed peace. When Kurt goes to Berlin, Keynes helps Kurt connect with important German bankers as news sources that launches his career as a foreign correspondent. Romance blossoms between Kate and Bill.

The two meet Left Bank historical characters including Janet Flanner, The New Yorker correspondent, writer Djuna Barnes, critic Solita Solano, poet Mina Loy, book shop impresario Sylvia Beach, literary editor Margaret Anderson and others. In the summer, Kurt visits Paris and speaks at the leading literary salon hosted by Natalie Clifford Barney. That night in a Montparnasse café, Barnes comes in looking for her girlfriend, who has left for New York with another woman. Kurt offers to buy her a drink and the two leave together. Barnes helps Kurt rewrite parts of his novel, re-shaping the heroine from idealized goddess to a brave, but war-worn, woman. Later Kurt returns to Paris with an almost-finished novel while Bill hosts a party celebrating Barnes' new novel which is a surprise bestseller in New York. In a late night jazz club, Barnes describes to much raillery her vision of a Surrealist drama entitled "The Economic Consequences of the Peace" based on John Maynard Keynes' book to an Our Crowd group of Left Bank writers and Surrealists. Barnes' play mirrors the larger theme of Kurt's novel: the story about the brave war and the peace that was lost in the 1919 Paris Peace Conference.

Just before the tenth anniversary of November 1918 Armistice, the novel comes to its dramatic close.