Jessica Chastain seems to be attracted to playing strong characters, including a CIA analyst in Zero Dark Thirty; the mission commander in The Martian; and, more recently, a lobbyist taking on the gun industry in Miss Sloane.

It’s no surprise, then, that she was drawn to the title role in The Zookeeper’s Wife, which opens in theaters nationwide on March 31. The film, based on a true story, revolves around Jan (played by Johan Heldenbergh) and Antonina Zabinski (Chastain), a couple who put their lives at risk to save 300 Polish Jews from the gas chambers.

Jan was head of the Warsaw Zoo, one of the finest in Europe. Families dressed in their Sunday best came from throughout the area to parade around the lawns, view animals and perhaps catch a glimpse of Antonina as she biked around the grounds, followed by a menagerie of animals with which she seemed to have a special connection.

After Nazi bombs destroyed the facility, killing many of the animals, the few valuable species that survived were transferred to Berlin for breeding purposes under the orders of Lutz Heck (Daniel Brühl), the Berlin Zoo director-turned-Nazi officer. The Zabinskis convinced Lutz to allow them to keep the zoo grounds open as a pig farm. Deciding to risk it all, the couple smuggle Jews out of the Warsaw Ghetto, hide them in the cages, tunnels and basements where the animals once lived and, ultimately, transfer them to safe houses.

“I wanted to portray Antonina because I love the compassion she exemplified and the heroism in that compassion,” Chastain said in an interview.

Chastain’s performance is a highlight of the film; if only the rest of the film were as good. Too many questions are left unanswered. For example, how is it possible that the troops billeted at the zoo where the Zabinskis continue to live don’t notice anything strange?

Yad Vashem recognized the Zabinskis as Righteous Among the Nations in 1965. The Zookeeper’s Wife—based on the book by Diane Ackerman that, in turn, is largely based on Antonina’s diary—does not sufficiently do them justice.