The biggest journalistic investigations often begin with the smallest of inquiries. Lisa Napoli’s new book, Ray & Joan: The Man Who Made the McDonald's Fortune and the Woman Who Gave It All Away, which is the product of five years of reporting, is no exception.

Napoli first came across Joan Kroc as an arts reporter for KCRW while covering a movement in Santa Monica to save “Chain Reaction,” Paul Conrad’s 26-foot tall anti-war sculpture of a mushroom cloud, from rust. Napoli was talking with Jerry Rubin, a peace activist who was leading the effort to restore the piece, when he mentioned that although the sculpture was anonymously donated, he suspected it was a gift of Joan Kroc, the wife of McDonald’s titan Ray Kroc. As a public radio reporter, Napoli knew Joan Kroc’s name well, as she’d donated $200 million to NPR in 2003. But beyond that hint, Napoli had no significant impression of the woman.

Napoli decided to look into Rubin’s claim, and was ultimately able to confirm that the sculpture was indeed created with financial support from Kroc. But she wasn’t able to find too much else about the personal life of the late philanthropist, who used the fortune she inherited from her husband to support a vast range of causes and institutions. But as Napoli encountered roadblocks in her initial inquiries, she became increasingly determined to uncover Kroc’s untold story.

“The more I learned about her sense of humor and passion and impetuousness, the more I fell in love with her. She’ the kind of woman I hope I’d be if I were a multi-multi-millionaire,” Napoli says. “She’s the woman I try to be now, without the endless bank accounts. She wasn’t this sort of dowager philanthropist, which one might presume when they hear ‘foundation’ or ‘estate’ or something like that. She broke a lot of rules; she was very unorthodox.”

At that point in her career, Napoli had already written a book, Radio Shangri-La, which chronicled her time helping start a radio station in the Himalayan kingdom of Bhutan, but she’d never written a biography. She joined the Biographers International Organization to help her navigate the unique challenge and dove head-first into research. Napoli reached out to McDonald’s right away, but the company “expressed absolutely zero willingness” to help, she says. Initially, Kroc’s family was also reluctant to participate, but eventually, Napoli was able to correspond with Joan’s daughter and meet with two of her granddaughters. But generally, Napoli said, “the family was not thrilled or excited about a book being written, in part because Joan fairly often said she didn’t want any reporters around.”

Napoli was ultimately able to find a lot of material in the archives of the Joan B. Kroc Foundation and in the archives of newspapers in San Diego, where Kroc lived. She also managed to locate characters from Joan’s world all over the country who had memories to share.

At first, Napoli set out solely to write a biography about Joan Kroc, but as she learned more about her, she decided that the scope of her project actually needed to be more expansive.

“The more I tried to piece together the story about Joan, I realized I couldn’t tell the story of Joan without telling the story of Ray and I couldn’t tell the story of Ray without telling the story of McDonald’s. Somehow these disparate threads twined together and I got hooked,” she says.

Her book, ultimately, is the story of a relationship, one that was as tumultuous as it was fascinating. Moviegoers this December will also get some insight into the Krocs in The Founder, which chronicles Ray Kroc’s acquisition of the McDonald’s fast food chain. But Napoli said her telling of the McDonald’s story is unique in that in puts Joan front and center, introducing the world to a figure whose contributions should no longer be obscure.

“I think she’s sort of this distant historical figure to people even though she only died 13 years ago. She’s just really not known,” she says. “The book is not really a correction [of her reputation], so much as putting her on the map, putting her history out there.”

Jordan G. Teicher is a journalist and critic based in New York City. He's been published by Slate, NPR, the New Republic and Wired, among other publications.