In the darkest days of the 20th Century, as the shadow of the evil that was the Holocaust fell across Europe, the courage of one woman was the difference between life and death for a few Jewish families from a little Ukrainian village.
Esther Stermer lived in that village with her six children until Nazi forces came in late 1941.
More than a thousand Jews were rounded up and sent to camps, where most died.
But Esther found another way.
Along with her family, including her sons Saul and Sam Stermer, 92 and 86 today, Esther spent nearly a year and a half underground, living in the pitch black of two vast caves in Ukraine, along with 36 other Jews, to escape Nazi persecution.
"The secret is that we were in trouble," Sam Stermer told ABC News. "But we never did give in."
It is an astonishing story, one of strength and survival from the Holocaust, brought to light 70 years later in the documentary "No Place on Earth." In October 2010, both Saul and Sam revisited the cave for the first time.
"It's a story about what people are capable of, both in love and achievement," Janet Tobias, who directed the film, said.
Saul and Sam credit their mother for saving their lives and keeping them safe for the more than 500 days they spent together in the darkness of the caves.
"We had a very smart mother," Sam said. "If I wouldn't have this type of mother, I wouldn't be alive."
So they made their own way, deep underground in nearby caves that run for miles, living in total darkness, like the bats and mice down there, and all they had was one another, and their own ingenuity.
"You went to sleep and you had a pillow and you covered up with good blankets," Saul Stermer said. "What else you want? You were in paradise."
For the Stermer family, the caves provided the freedom they were robbed of during the war.
"We were free men," Sam said.
Once, German SS soldiers raided the first cave they hid in and their mother, Esther, faced them down.
"She came out and stood in front of the guy, the guy with the gun like this," Sam said. "And she says, 'What are you afraid of here? The Fuhrer is gonna lose the war because we live here?' Can you imagine a Jewish woman to say just the word 'Fuhrer'?"
They foraged for food at night, built showers and latrines deep underground until finally, in April 1944, the Russian Army liberated the area, and the five families (38 Jews in total) came back into the light, and back into a life out of the abyss.
Last year, for the film, they returned to the cave.
After the war, Saul and Sam Stermer made their way to Canada, founded a successful contracting business, where they still go to work each day.
The ordeal of living a life underground, spending countless nights lying in a cavernous space, shaped how the Stermers lived their lives.
"We were just happy to survive," Sam said. "Then life started to turn normal, and that's it. We tried to get ahead. We tried to survive after the war."
Today, these 38 survivors now have more than 125 children, grandchildren, and great grandchildren. They have a story, out of the darkness, where they found life.
"This is a completely different story, because it was a happy ending," Saul said.