Agnes Poirier grew up on film sets and in the wings of theaters throughout Paris thanks to her father’s acting career and her mother’s being a playwright. A passion for politics led to a Ph.D. in international history at the London School of Economics, but she eventually left academics to pursue journalism. She’s worn many hats throughout her career, each reflecting part of her diverse background: writer, critic, foreign correspondent, script reader, adviser to the Cannes and Venice film festivals, and a go-to resource for the British media on all things France. However, with her latest project, Left Bank: Art, Passion, and the Rebirth of Paris: 1940-50, Poirier has found the perfect outlet to weave together all her expertise.

An ambitious “reconstruction,” as Poirier likes to call it, Left Bank is a history of the artists, writers, and philosophers that lived through German occupation and then transformed Paris’ Saint-Germain-des-Prés into an existentialist playground with their debauchery and lively debates. But Poirier goes much further by re-creating intimate moments between figures like Simone de Beauvoir and Jean Paul Sartre with the passion and eye of a novelist while using the skills of a historian to stay grounded to facts she collected during more than two years of research.

“I became obsessed with details,” Poirier says. “I wanted to know what they were doing and at what time...the color of the ink [DeBeauvoir] was using, the brand of cigarettes, what they were eating, what they were drinking. It became so much more real because of those details.” Poirier pored over archived diaries and conversations and met with still-living figures like singer Juliette Greco. In cross-referencing her sources, she realized she could pinpoint the exact days when American writer Saul Bellow and DeBeauvoir must have crossed paths, as they would have been on the same street at the exact same time.

While Poirier’s attention to detail offers revelations about well-known figures—DeBeauvoir fans will either be horrified or amused to learn that she spent the beginning of WWII lounging in the countryside, reading trash crime fiction, and debating the merits of a menage à trois with a friend—she also unearths figures who were towering at the time but are now largely forgotten, like writer Edith Thomas, journalist Theodore White, or Gerhardt Hellert, the complicated Nazi who both censored and supported the existentialists’ earliest plays and publications. “One character would lead me to another,” says Poirier. “It was a constant journey from one surprise to another.”

The biggest surprise for readers, however, might be how contemporary these remarkable people seem today. Brexit, Trump, and France’s contentious election had yet to happen when Poirier began editing, but many quotes she has unearthed from Sartre or Camus feel like they were written in direct reaction to them. “They breathed politics,” says Poirier. “Politics was everything.” Her characters are constantly engaged in lively debates about polyamory, abortion, and the danger of partisanship. Sartre and Camus strived, eventually in vain, to found “The Third Way,” a political compromise between the hard-line communists and right-wing parties warring over Europe’s future. “They were even more brilliant than I thought they were,” Poirier says, musing on the suddenly prescient discourse.

This all helps to reinforce something central to Poirier’s book: that the lasting influence of the thinkers featured in Left Bank can’t be overestimated. The remaining cafes and jazz clubs of the time are still full, with crowds drawn to the figures that first made them famous. Even born-and-raised Parisians like Poirier herself have felt the allure. She spent her high school years dancing at Le Caveau de la Rochette and says that on her first day of university, “I spent my lunch money to have a double creme at Le Café des Deux Magots, surrounded by American tourists.” Today, after spending years getting into their heads, she now sees the effects of these thinkers everywhere: “They still affect how we think, how we dress, and how we love, certainly in France....It was Paris.”

Rhett Morgan is a writer and translator based in Paris.