Heroism can come from the most humble places.

That’s the message behind The Zookeeper’s Wife, the story of Antonina and Jan Żabiński’s heroic acts that saved around 300 Jews after Poland was invaded during World War II. Based on the book of the same name by Diane Ackerman, this big-screen adaptation finds Jessica Chastain playing a compassionate woman who helped save hundreds of lives alongside her zookeeper husband.

“Antonina was an ordinary woman who opened her doors to strangers,” Chastain tells PEOPLE. “She sacrificed her safety, she sacrificed the safety of her children and everything that she loved to protect others. She created a sanctuary of her zoo, and not only did she save their lives, but she brought love and fostered hope and bolstered their spirits.”

Jan — played by Johan Heldenbergh — and Antonina lived at the Warsaw Zoo with their young son Ryszard and were compelled to protect the Jewish population from the German invasion. After Warsaw was bombed in 1939 and the majority of their exotic animals either died or were confiscated by German zoologists, the Żabińskis started hiding Nazi victims in the empty animal cages once the Warsaw Ghetto was established.

The couple devised a plan to turn the zoo into a pig farm in order to keep it operational, and it became just one of several ways Jan began smuggling people out of the ghetto. After he got permission from the Nazis to use the garbage inside to feed the pigs, the zookeeper would hide people in barrels underneath the garbage and bring them to the zoo. Jan also had access to the ghetto as a worker of the labor union and he would bring people out one or two at a time, pretending they were his workers. Once they got back to the zoo, the Żabińskis gave them identification and helped them find a place they could flee to.

Chastain as Antonina

But while most only remained for a few days, and mostly stayed in the various cages, the Żabińskis also housed families in their basement and home. Stephania Tiroshe’s family hid in the zoo for over two months — the longest time anyone stayed. Tiroshe was just 7 months old when the war started and was 3 when her mother escaped the ghetto with her brother in 1943 and sought solace with the Żabińskis. The holocaust survivor tells PEOPLE how Antonina devised a clever system of signals to alert the houseguests of danger when German soldiers were nearby.

“I remember that we ran around the house when we could, because usually we were in the basement or in the cages,” Tiroshe recalls. “But what I remember most is that the Germans used to come from time to time, and when the people at the gate saw them coming, they gave a signal to the villa and Antonina used to sit by the piano and start to play and my brother and I knew we had to hide. My brother would always say, ‘Come, come, we have to hide so they don’t kill mom.’ ”

Though Tiroshe was too young to fully understand why they needed to hide, she says she clearly remembers fearing that the soldiers would kill her mother if they were found. Out of the 300 Jews the Żabińskis housed, only two didn’t survive the war.

 

The Żabińskis carried on with their life during this time, with Antonina giving birth to their daughter Teresa in 1944, near the end of the occupation. Jan also stayed active in the resistance and led the underground Polish army against the Nazis. He stockpiled weapons in the cages that weren’t used to hide people and was even captured and sent to a German prison in 1944. The zookeeper survived, however, and the family was reunited at their zoo after the war, reopening it in 1949. Jan resigned as director two years later.

Antonina, who died in 1971, and Jan, who died in 1974, were recognized by the State of Israel as the Polish Righteous Among the Nations for their actions. The Warsaw Zoo remains open in Poland.

But while they saved hundreds of lives, Teresa tells PEOPLE her parents didn’t see themselves as heroes. “My parents told me that they did only what should have been done — it was their obligation to do that,” she says. “They were just decent people. They said decent people should do the same, nothing else. I’d like as many people as possible to understand what actually happened here in Warsaw during the war, and how much humanity and love can do.”

Chastain with Teresa at the Warsaw premiere

Ackerman, the book’s author, echoes Teresa, saying that it’s Antonina’s compassion and bravery that shines through in the film.

“Her story’s been lost in the seams of history, as women’s stories very often are, but she was profoundly heroic” Ackerman tells PEOPLE. “She risked her life every single day, but she didn’t pick up a gun and shoot someone. She wanted to keep the people hiding at the zoo alive with their humanity intact so that they wouldn’t be so traumatized by the events that they would be unable to live their lives afterwards. She was very empathic and concerned about the people in her care. It’s a different model of heroism.”

 

from PEOPLE.com