Vera Sung, left, Jill Sung and Thomas Sung in “Abacus: Small Enough to Jail.” (Courtesy of Sean Lyness)

In a David-vs.-Goliath matchup, a bank is an unlikely candidate for the underdog.

But that’s the story that celebrated documentarian Steve James tells in his latest film, “Abacus: Small Enough to Jail,” which follows the five-year legal saga of the only bank prosecuted for mortgage fraud in the aftermath of the 2008 housing crisis: a family-owned community bank in New York City’s Chinatown.

The film, which comes out in Washington theaters Friday and on “Frontline” this fall, focuses on the bank’s owners, the charismatic Sung family, who argue over legal strategy, laugh over meals and shed tears over the fate of their legacy.

“A lot of the films I’ve done, if not all, have been about people at important junctures of their lives,” said James, director of 1994’s “Hoop Dreams,” one of the most acclaimed documentaries ever made. “Either trying to make a dream happen, or facing adversity in some fashion, and having to either overcome or not.”

Thomas Sung founded Abacus in 1984 to cater to the Chinese and Chinese American community. One of his four daughters, Jill, later took over as CEO and president. Another, Vera, serves as the bank’s director.

Many of the bank’s customers work in Chinatown’s cash economy, meaning finding paperwork to secure home loans can be a challenge. In 2009, Vera and Jill Sung discovered a fraudulent scheme in which one of the bank’s loan officers misrepresented borrowers’ income on mortgage applications. Within days, the bank fired the loan officer and investigated and reported the incident. After a borrower filed a complaint to authorities, the bank handed over stacks of documents.

Still, it became a target. A handful of former employees allegedly involved in the scheme were handcuffed and paraded before television cameras in a chain-linked group — and were indicted on 184 counts, including mortgage fraud and conspiracy. The fired loan officer became the prosecution’s star witness.

In announcing the indictment, Manhattan District Attorney Cyrus Vance Jr. said Abacus engaged in “a systematic and pervasive mortgage fraud scheme” and sold millions of dollars in fraudulent loans to Fannie Mae.

Fannie Mae, the film takes pains to point out, didn’t end up losing money on those loans.

“The way we saw it, it was basically an indictment of the community,” Jill Sung said in an interview.

Director Steve James: “A lot of the films I’ve done, if not all, have been about people at important junctures of their lives.” (Greg Gorman)

The Chinese-language press covered the story daily, but the mainstream media largely ignored it, James said. He found out about the impending trial from producer Mark Mitten, a friend of Vera Sung’s.

“After I got to know the Sungs and heard more about their side of the story and their case, it became pretty clear pretty quickly to me and the rest of our team that this just doesn’t seem right,” James said. “The film makes no bones about being in the Sungs’ corner. We don’t go along an objective tone.”

The Sungs initially argued about whether to let James make the documentary.

“I wasn’t for it,” Jill Sung said. “I felt like there was just too much going on with the trial, and I was afraid if the trial didn’t work to our favor, what would the documentary be saying?”

But Vera Sung said it was “important to share this story, not for ourselves but for the effect it has had on our community. And also, it’s rather eye-opening, to say the least, about the criminal justice system, big banks versus smaller banks.”

The family came to a consensus, and James soon developed a good rapport with the Sungs, whom he said he “fell in love with pretty much immediately.”

It wouldn’t be an easy story to tell. The crew didn’t have access to the courtroom, so they hired a sketch artist and paired the images with voice actors reciting from the trial transcript. There were 7,000 pages of testimony to sort through. And they had no idea how long the trial would take.

James’s team made repeated attempts to get the prosecution on camera. Prosecutors and two jurors finally agreed once the trial ended.

Translating complex financial matters into dramatic and accessible on-screen stories can also be a daunting task.

“I remember being fascinated about that, but also scared. Would people find this interesting? The pettiness of the charges contributed to the fact that nobody found this important enough to report on,” James said. “If a big bank had been on trial, it would have been huge.”

As the film recounts, Thomas Sung started the bank to serve an underserved population; as a Chinese immigrant, he previously had difficulty getting loans from banks himself, despite also being an American-educated lawyer. In the film, Sung walks around Chinatown, shaking hands with activists, eating in local restaurants and visiting educational centers.

Although the 2008 mortgage crisis inflamed people’s passions about banks, Sung’s mission was “to serve people, so that’s what we understood banking to be ever since were little,” Jill Sung said.

That the state prosecuted a small community bank rather than behemoth financial institutions that dealt with subprime mortgages made the story even more important, James said.

Matt Taibbi, author of a book about America’s wealth gap, says in the film that while big banks were too big to fail, Abacus was small enough to jail. “If you were going to pick a bank to pick on, a family-owned company wedged between a couple of noodle shops in Chinatown is about as easy a target as you can pick,” he adds.

But Vance stands by his decision. “I think Americans were upset that the security against which loans were made were often fictitious. And at Abacus, there was some truth to that, too,” Vance says in the film. “It’s clearly not a big, big bank. And clearly it was not representative of the entire financial community — but I think the principle was the same.”

Jill Sung, left, Vera Sung, and Thomas Sung. (Courtesy of PBS Distribution)

Legal issues aside, the film’s anchor is a loving family full of strong, charming personalities.

Many audience members will relate to the family dynamics, from matriarch Hwei Lin Sung’s funny and candid declarations — “she steals the movie,” James said — to one of the Sung sisters trying to get a word in edgewise as the others debate.

With all the drama enveloping their lives, the Sungs soon forgot about the cameras. One sister, Chanterelle, came to find the filmmakers’ presence “calming” as she could tell them what she was feeling “without expecting any judgment, because they were just documenting it,” Jill Sung said.

The trial also brought the Sungs together, as they took time off to work through the legal battle as a group.

“I said, remember these days, these moments, where we’re actually together every day,” Vera Sung said.

Now that “Abacus” has hit the festival circuit, the film’s subjects have found seeing themselves on the big screen quite surreal. But Thomas and Hwei Lin Sung still like watching it with others.

“It’s so funny — every time, I say, ‘Do you really want to sit through this?’ And every time they go, ‘Yes! We want to watch it!’” Vera Sung said. “It feels like you’re going through it with the audience. It’s very cathartic.”

Unrated. At Landmark’s E Street Cinema. Contains strong language. In English, Cantonese and Mandarin with subtitles. 88 minutes.