A new Netflix documentary has brought one of World War II’s most astonishing survival tales back into the spotlight: the true story of a 7-year-old Jewish girl who spent over a year hiding in the filthy, rat-infested sewers beneath Warsaw after Nazis forced her family underground.

The film, titled Underground Angel, premiered last week and quickly climbed Netflix’s Top 10 in multiple countries. It chronicles the harrowing journey of Krystyna Chiger, who, along with her parents and younger brother, escaped the liquidation of the Lvov Ghetto in 1943 and descended into a labyrinth of waste tunnels to evade capture.

What makes Chiger’s story stand out isn’t just the duration of her subterranean ordeal — 14 grueling months — but the quiet acts of bravery she displayed as a child in conditions that broke grown men.

The documentary opens with archival footage of the Lvov Ghetto in western Ukraine, where over 100,000 Jews were confined under brutal Nazi control. As the SS began systematic deportations to death camps, a small group of families paid a Polish sewer worker named Leopold Socha to guide them into the city’s drainage system.

Socha, initially motivated by money, led 20 people — including the Chiger family — through a manhole into a world of darkness, stench, and constant danger. The group lived on ledges above flowing waste, sleeping in shifts, eating stolen bread, and drinking water filtered through cloth.

Krystyna, just 7 when the ordeal began, became the emotional center of the survivors. Her mother, Paulina, later recalled in interviews featured in the film that Krystyna never cried — not once — despite the horrors around her.

“She understood that silence meant life,” Paulina says in a 1990s recording played during the documentary. “One sound, and the Germans would find us.”

But it was Krystyna’s actions during a near-disaster that cemented her legacy.

Six months into their hiding, heavy rains flooded the sewers. Water rose to the group’s waists, then chests. Panic set in. Adults screamed. Children wailed. The escape ladder had been swept away.

That’s when Krystyna, barely tall enough to keep her head above water, remembered a narrow service pipe she’d explored during rare moments of play. Holding her brother Pawel’s hand, she led the group single-file through the freezing tunnel to higher ground.

Without her memory and calm leadership, historians featured in the film say the entire group would have drowned.

“Children often adapt in ways adults can’t,” says Dr. Elena Rosenberg, a Holocaust scholar at Yad Vashem. “Krystyna’s mind mapped the sewers like a playground. That spatial memory saved 20 lives.”

The documentary doesn’t shy away from the grim reality. Rats the size of cats gnawed at their feet. Dysentery claimed several members. One man, driven mad by claustrophobia, tried to climb back to the surface and was shot by German patrols.

Socha, the sewer worker, became an unlikely hero. Though he began the arrangement for payment, he continued bringing food and supplies long after the money ran out — even selling his wife’s jewelry to buy bread. The film portrays him as a flawed but redeemed figure, a Catholic man who risked execution to protect Jews.

Netflix’s adaptation draws heavily from The Girl in the Green Sweater, Krystyna’s 2008 memoir co-written with her father, Ignacy. The title refers to the only clothing she wore for over a year — a hand-knitted green sweater her mother refused to let her remove, fearing she’d freeze in the damp tunnels.

Archival interviews with Krystyna, now in her late 80s and living in New York, form the emotional backbone of the film. She speaks softly, without bitterness.

“I don’t remember being scared,” she says. “I remember being hungry. And I remember my mother’s voice telling me to be quiet. So I was quiet.”

The production team faced unique challenges recreating the sewer environment. Director Robert Marshall built a 200-foot replica tunnel in a Warsaw warehouse, complete with running water and controlled rat populations (trained animals, under strict welfare protocols).

“We wanted authenticity without exploitation,” Marshall told reporters at the premiere. “The sewers weren’t just a setting — they were a character. Dark, alive, unforgiving.”

Critics have praised the film’s restraint. Unlike many Holocaust dramas, Underground Angel avoids graphic violence, focusing instead on psychological tension and human connection. The New York Times called it “a masterclass in less-is-more storytelling.”

Viewers, however, have been less restrained in their reactions. Social media is flooded with stunned parents sharing screenshots of their kids watching Krystyna’s story.

One viral TikTok with 3.2 million views shows a mother asking her 8-year-old daughter, “Could you be that brave?” The child pauses, then whispers, “I’d try.”

The documentary also addresses a lingering controversy: Socha’s motivation. Some historians argue he was paid until the end; others insist his actions transcended money. The film presents both views without judgment, letting viewers decide.

Krystyna herself refuses to label Socha a saint.

“He was a man,” she says in the film. “A complicated man who chose to do the right thing when it mattered. That’s enough.”

The Chiger family emerged from the sewers on July 27, 1944, when Soviet troops liberated Lvov. Of the 20 who entered, 10 survived — including both Chiger children.

Post-war, the family emigrated to Israel, then the United States. Krystyna became a dentist, married, and raised two sons. She only began speaking publicly about her experience in her 60s, after her father’s memoir was published.

Netflix’s timing couldn’t be more pointed. As antisemitic incidents rise globally, Underground Angel serves as both warning and testament. The platform reports over 12 million hours viewed in the first five days — numbers rivaling major fictional releases.

Educators are already incorporating the film into curricula. The Anti-Defamation League partnered with Netflix to create discussion guides for middle school students, emphasizing themes of resilience and moral courage.

Perhaps the most powerful moment comes near the end. Adult Krystyna returns to the Lvov sewers — now a tourist site — with her granddaughter. She points to a rusted pipe.

“That’s where I found the way out,” she says. “Not just for us. For hope.”

The camera lingers on the child’s face — wide-eyed, silent — as water drips in the background.

Underground Angel isn’t easy viewing. But as one survivor in the film remarks, “Some stories must be hard to hear, so they’re never forgotten.”

For Krystyna Chiger, the little girl in the green sweater, survival wasn’t about heroism. It was about the next breath, the next step, the next day.

And 14 months later, she took those steps back into sunlight.