Sheila Nevins admits that she stole the book.

When the legendary documentary filmmaker and HBO executive arrived early for a program at the Museum of Jewish Heritage where she was introducing a film, she was shown to the library to wait, alone. She spotted a shelf of children’s books, and one in particular, David Adler’s “The Number on My Grandfather’s Arm,” piqued her curiosity. The book had been published about 25 years earlier, and she immediately saw the possibility of a documentary.

“I put the book in my pocketbook, read it that night and was haunted by it,” Nevins told The Jewish Week. “I knew that the story now would have to be about a great-grandfather. I knew I had to hurry, or soon there wouldn’t be any survivors left.” Nevins, who is just stepping down after 38 years as president of HBO Documentary Films, has produced more than 1,000 documentaries that have won Emmy, Peabody and Academy Awards, and she has won more individual Primetime Emmys than any other person.

“The Number on Great-Grandpa’s Arm” airs on HBO on Saturday, Jan. 27 at 6 p.m., to mark International Holocaust Remembrance Day.

In the documentary film, a 10-year-old boy, Elliot Saiontz, asks questions of his spirited great-grandfather Jack (formerly Srulik) Feldman, who was imprisoned by the Nazis at work camps and then at Auschwitz. Although 80 years separate the two, the camera highlights their intimacy: They talk and walk, often holding hands, as though they don’t want to let go of one another.

Documentarian Sheila Nevins.

“Documentaries tell you when you’re not telling the truth. You can’t fake that love,” Nevins says.

Produced and directed by Amy Schatz, with Nevins as executive producer, the film features Saiontz’s and Feldman’s conversation, filmed two years ago, interspersed with hand-painted watercolor animation by Jeff Scher, rotoscoped from actual photographs and historical footage. There are scenes of Feldman’s happy childhood in Sosnowiec, Poland, as well as the final death march from Auschwitz before he was liberated.

Feldman, the son of a successful capmaker, was arrested as a young teen and never saw his parents again. Once, his father sent him a cap, and he knew that he’d find money hidden in the brim, and that helped secure some extra scraps of food. After the war, when he made his way to America, he opened Jack’s Fish Market in upstate Rochester. In a scene in the film when the pair visit the shop, a worker points to the number on Feldman’s arm and says that the man knew hunger, and never turns away anyone from his shop.

“His story has changed a lot of people,” Saiontz says on camera. “You need to know it to understand and stop it from happening in future generations.”

As to whether watching films can change people, Nevins says, “If you can create empathy, then you can change behavior, and ultimately behavior changes minds.”

She says that at preview showings, children don’t cry but their parents do. “Adults cry for what they remember,” she says. “Children are interested in what they don’t know.”

HBO and the museum are preparing an educational initiative tied to the film, featuring other cross-generational conversations.

While she is stepping down at HBO, Nevins will not stop making films. She’s very interested in making a documentary about anti-Semitism. While she says she doesn’t understand it, she has witnessed it in her work and in the outside world.

Both Saiontz, now in the sixth grade in Westchester, and Feldman will be present at a preview of the film at the Museum of Jewish Heritage on Sunday, Jan. 21. (And so will Nevins, so watch her bag.)