Although Ms. Nevins has a magnetic quality and thought of becoming an actress, after attending Barnard College and getting an M.F.A. in directing from the Yale School of Drama, she is more comfortable in her apartment, editing. She finds socializing and small talk draining. She prefers chronicling underdogs to celebrities, and when I ask which documentary is her favorite, she pulls out a DVD from her bag about the fight to save a brown pelican soaked in oil found in the waters off New Orleans after the BP spill in 2010.

“I do have a philosophy about documentaries, which is that I really do believe that almost everybody has a story,” she says. “I love ordinary people. And they’re often very heroic. And very interesting. I don’t like fame. I’m not interested in famous people. I don’t trust the sameness of the story you get from celebrity. The few times I’ve had to deal with celebrity, I’ve read the same thing they say somewhere else.”

Mr. Plepler says that Ms. Nevins’s “chutzpah and smarts” do not allow her to kiss up to stars. When the inimitable Mike Nichols came in several years ago to pitch a documentary, Mr. Plepler says he listened with reverence. Ms. Nevins, however, said flatly, “I don’t think it’s a good idea and here’s why.” There was an uncomfortable pause of about 20 seconds before Mr. Nichols spoke up: “You know, you’re absolutely right.”

Ms. Nevins’s heart is with the down-and-out or afflicted.

“Sheila is the social conscience of corporate television,” says Alexandra Pelosi, who has made 11 documentaries with Ms. Nevins. “Who will carry the torch now? She puts stuff on TV that is not fun to watch.” From her perch atop the world of documentary film, Ms. Nevins has deftly navigated subjects including substance abuse (one such project in 2007, “Addiction,” was inspired after watching her only son’s battle and recovery with drug addiction), homeless children, and pedophile priests who preyed on deaf children in Milwaukee.

Right now she’s obsessed with examining the motivations of the 650,000 Alabamians who voted for Roy Moore, much in the same way she once needed to understand Barack Obama’s haters.

“She’s in a beautiful apartment on the Upper East Side now, but deep down in her soul she is still the little girl who grew up on the Lower East Side,” Ms. Pelosi says. “She doesn’t get her ideas at cocktail parties. She gets them talking to grocery-store clerks or when she visits women in prison. She wants filmmakers to get out of their comfort zones. She has a punk-rock streak.”