Returning to the Ukrainian cave 67 years later — the raw space that protected him from deadly persecution by Nazis in World War II — the survivor makes a simple request: Turn off the lights.

The artificial illumination shining underground shuts off, giving way to pitch blackness. Saul Stermer relaxes. He is home.

This extraordinary moment comes near the end of “No Place On Earth,” a new Holocaust documentary telling a story that almost feels like fiction. But survivors are here to tell the tale, for it is very real.

The film revisits 38 cave inhabitants who lived as a small community in dark, humid conditions where no humans had lived before.

And not just for a day or a month. Most of the survivors, ages 2 to 76, persevered underground for more than 500 days before returning to the surface in 1944.

“We survived as a complete family,” said Sonia Dodyk Hochman, not quite 5 when she descended into the first cave with her clan. “That was unheard of.”

When she and her family finally crawled out into the sunlight, Sonia covered her eyes and told her mother someone had forgotten to “close the candle.” The little girl didn’t remember sunlight.

Many who lived in the two Ukrainian caves had childhoods almost impossible to fathom, and it was never certain they would reach adulthood. But three of the survivors attended the film’s Midwest premiere last week at the Illinois Holocaust Museum. Today, they’re seniors, speaking of those long-ago days, which are never as distant in their minds as they are in time.

“Whenever we got together as a family, we would talk about it,” Sam Stermer said. “[We] would even say, ‘We’re not going to talk about it this time,’ but in the end, we talked about it every time. For the last 70 years.”

The stories, however, stayed within the family. Grandchildren went to bed by those stories; children were exposed to them repeatedly. The family’s matriarch, Esther Stermer, wrote a book, which the family translated into English in the 1970s, but even the book remained inaccessible to the public.

For the families’ stories to move from darkness to light required another sort of miracle.

Amateur cave explorer Christopher Nicola, looking for his own ancestors’ history, supplied it. He stumbled across artifacts in one of the caves near the Bilche Zolote village: a shoe, buttons, stoves, earthen pottery and more.

In “No Place On Earth,” director Janet Tobias cuts between Nicola’s effort to unravel the mystery, and the five families, who moved from the five-mile Verteba cave to the 77-mile Priest’s Grotto cave. The documentary augments astonishing firsthand accounts from survivors with brief re-created scenes. (The technique may remind some viewers of the 2003 mountain-climbing documentary “Touching the Void,” which also augmented interviews with re-created scenes, featuring actors who do little speaking.)

Women never left the cave, while men risked their lives by going to the surface to forage for food and other resources.

“The women used to sit and wait,” said Sima Dodyk Blitzer. “We never knew for sure if they would come back.”

The makeshift community of cavers created its own rules. They learned to cook underground, rationing food as people grew hungrier. They often slept 18 or 20 hours a day. When the group sensed impending danger, they worked together, digging out an emergency escape exit, which would become necessary for survival.

Not everyone survived. Sol Wexler lost his mother and a sibling. Sima and Esther were hauled away, the former believing at the time they would be shot.

Standing front and center in almost all the Stermers’ survival episodes are Esther, who led her clan underground knowing they could not stay home anymore, and Nissel, the older brother who relayed valuable news from outside and provided resourcefulness and ingenuity to meet unimaginable challenges.

“They turned themselves into world-class cavers,” Nicola said. “It’s hard for experienced cavers to survive underground for a year.”

Sima and Sonia vowed never to revisit Ukraine or its caves. But they relented, in part because they wanted to see the movie made, but also to thank the caves for saving their lives and their family members’ lives. The cave came to mean safety for most of the children who lived there; darkness below was their protection, the light above their vulnerability.

The movie’s expedition back to Ukraine included not just survivors, but also their children and grandchildren. Fewer than 5 percent of Jews survived in Ukraine, one of the deadliest places for them during the Holocaust.

“I feel I did something good,” Nicola said, about unearthing this slice of Holocaust history. “I went to the Ukraine looking for my family’s story, and I found someone else’s.”

And the story he found, much to his surprise, had a relatively happy ending. “We beat the odds,” Sonia said. “They did not get us. We were the master of our own fates.”