Such questions were, of course, examined - and with passion - immediately after the liberation of Paris. At the time, the imperative was to punish those artists and writers who had supported the occupying power or the puppet regime in Vichy, those deemed to have failed both their nation and their peers. But then, as now, the judgments were not clear-cut. Did working during the occupation automatically mean collaboration? Should any writer be sanctioned for the "crime" of an opinion? Do gifted painters, musicians or actors have a duty to provide ethical leadership? The search for answers became the starting point for this book.

Many French believe that the occupation is still a taboo subject: French friends warned me that my inquiries would be met by suspicion, embarrassment, even silence. I did not find this to be true. Since the early 1970s, when Robert O. Paxton published his book, Vichy France: Old Guard and New Order, 1940-1944, the myth of la France résistante has crumbled. Books have been written on every aspect of the occupation. Through movies like Marcel Ophüls's The Sorrow and the Pity and Louis Malle's Lacombe Lucien, the French public also learned that collaboration and self-preservation were stronger instincts than resistance.

In my case, I sought out artists, writers and others who witnessed the "dark years". Well into their eighties or even older, they all agreed to see me and, I believe, responded openly and frankly. Their testimony was crucial in demonstrating that life during the occupation was not a still photograph in which one moment represents all others; it was a constantly evolving drama, a teeming stage where loyalty and betrayal, food and hunger, love and death, found room to coexist, where even the line separating good and bad, résistants and collaborateurs, seemed to move with events. This was no less true in the world of culture. Its leading players behaved much like the rest of the population, except that, with them, more was at stake: their artistic calling made them role models and, as such, they were held to higher standards of propriety.

The main actors have now gone, yet all around me the décor stands largely unchanged. The very streets and buildings of Paris still carry the memory of those who peopled the stage seven decades ago. Often, while writing this book, I felt the past was my companion. Just a short bus ride separates the desk where I did my writing from the places it describes. It is both easy and hard to imagine the Wehrmacht marching down the Champs-Élysées, the swastika flying in the Place de la Concorde, the Louvre desolate and stripped of its paintings, German uniforms filling boxes at the Paris Opera. The Hôtel Lutetia on the Left Bank bears a double scar: from 1940 to 1944, it was the Gestapo's Paris HQ; then, in 1945, it became the reception center for returning prisoners-of-war and deportees. In a few cases, the décor has changed. Across from the Lutetia, the old Prison of the Cherche-Midi, so convenient for the Gestapo and so feared by its enemies, has been demolished and replaced by the kind of glass-and-steel anonymity that has no history.

Around my office in the 6th arrondissement, memories are even fresher. On my street, rue Monsieur-le-Prince, the early resistance group, the Musée de l’Homme network, held meetings at No. 30. One block away, a German-language book store catering to the Wehrmacht once stood on the place de la Sorbonne. That square was home to Jean Galtier-Boissière, a satirist who kept the sharpest and wittiest journal of the occupation. To the north, on the rue du Sommerard, a plaque outside a primary school remembers those pupils who were "deported from 1942 to 1944 because they were born as Jews, innocent victims of Nazi barbarity with the active complicity of the government of Vichy." Running past the square is the boulevard Saint-Michel, still pockmarked from intense fighting during the insurrection of Paris.

Nearby, the French Senate was the Luftwaffe headquarters and, behind it, the last tank battle in the city was fought in the Luxembourg Gardens. On many a wall, plaques record where young fighters died. And every year on August 25, the anniversary of the liberation, these fallen are remembered with bouquets of flowers.