“I don’t know anything about their youth — when they smoked their first cigarette, how they fell in love, what songs they listened to — because, after they escaped, it became like a traumatic memory. So they cut it out of their heads,” says Petzold, after a New York Film Festival screening of his new feature, “Barbara,” set in 1980 East Germany. “Me and my two brothers were always a little bit irritated by that. But after the wall came down, they started telling us stories about their past. At that moment, I knew that they had lost their youth.”

Indeed, for a country that existed for 41 years, stories about East Germany, says Petzold, seem to have receded into the shrouded mists of history — somewhat ironic considering the oppressive surveillance state it was.

Having made four previous films set in post-Berlin Wall-era East Germany, Petzold became increasingly fascinated with exploring the culture and everyday life of a fading East German past and the wounded psyche of its people.

“The German Democratic Republic has vanished now. It’s treated like a place in ancient stories about a country far, far away,” says Petzold, 52, between puffs on a cigarette sitting on a terrace outside Alice Tully Hall at Lincoln Center. “And when a country is far, far away, I think then cinema has to come and tell those stories.”

Petzold tasked himself with telling one of those stories. “Barbara,” which opens in the Boston area on Friday, centers on a young doctor (played by Nina Hoss) who rankles the authorities when she applies for an exit visa from the German Democratic Republic. As punishment, Barbara is banished from a prestigious hospital post in East Berlin to a gloomy pediatric facility in a small northern hamlet. There, she’s spied on and harassed by the menacing local Stasi officers, who chronicle her every move. Broken, guarded, and suspicious of potential informants, Barbara methodically bides her time and plots an escape from the country, aided by her West German lover, Jörg, with whom she rendezvous for clandestine trysts.

Despite the wall she’s built up around her, Barbara remains compassionately dedicated to her patients, connecting in particular with a rebellious teenage runaway and the case of a suicidal young man. Most dangerously, she finds herself drawn increasingly to the hospital’s head doctor, Andre (Ronald Zehrfeld), who reaches out to her in friendship as a kindred spirit. But Barbara is suspicious of his true intentions and wary of betrayal. She keeps her distance, fearful that he may be a Stasi informant. Yet the attraction between them continues to grow, and her loyalty to her patients tests her resolve to flee.

Consumed by paranoia, Barbara has adapted the techniques of her Stasi oppressors.

“The dialogue between them is like an interrogation,” Petzold says. “Throughout the whole movie, all the lines from her are spoken as questions. The couple is infected by the oppressive state. So in their infected state, how can they find words of love and trust? The relationship is for me like an adventure. As they talk to each other, they scan each others’ faces and make a new language of love out of this scanning, out of this mistrust.”

As part of his preparation process, Petzold typically screens films for his cast and crew that might provide connection points and touchstones for their characters. To capture the elusive dynamic between the couple, Petzold had the actors watch the 1944 Howard Hawks film “To Have and Have Not,” in which Humphrey Bogart and Lauren Bacall play wartime lovers suspiciously trying to suss each other out as they dodge the secret police. A flirtatious guessing game unfolds as they’re forced to read between the lines and look for hidden meanings.

Petzold also had the cast watch William Friedkin’s “The French Connection,” Rainer Werner Fassbinder’s “The Merchant of Four Seasons,” Roberto Rossellini’s “Stromboli,” and several films by Claude Chabrol. The 1971 thriller “Klute,” directed by Alan Pakula, was referenced for a sensual dinner scene between Jane Fonda and Donald Sutherland’s characters when it becomes clear that they’ve fallen for each other.