There are plenty of mysteries still swirling around Jeffrey Epstein, the convicted sex offender who’s newly indicted for sex trafficking (he’s pleaded not guilty). But the biggest unanswered question remains how he made the nearly $600 million that he and his attorneys listed on his unaudited and unverified financial statement. In order to find out how he amassed his fortune, it may take subpoenas from the U.S. Attorney’s Office in the Southern District of New York to Wall Street types in Epstein’s inner circle—people such as Leslie Wexner, the billionaire founder and CEO of L Brands, Glenn Dubin, the billionaire cofounder of the hedge fund Highbridge Capital Management, and Leon Black, the billionaire founder of Apollo Global Management, the private-equity behemoth.

While we await subpoenas and depositions—if they ever come remains to be seen—there is a road map of sorts in the form of Epstein’s so-called “little black book,” 92 pages of names, emails, and phone numbers of people Epstein knew, or wanted to know, but in any event had detailed information about. Wall Street people comprise a significant amount of the entries. “He was a kind of wholesale collector of people, including people he didn’t know,” one of the Wall Street guys in the black book tells me. “I guarantee you that 90% of the people whose names are in his book, he’s not in their book. Many of these people don’t even know him.”

What the book tells us is that Epstein knew, or aspired to know, some of the biggest names on Wall Street and in Washington. Sure there are the Trumps—Donald, Ivana, and Ivanka—and Bill Clinton’s surrogate Doug Band in the book. But once you get past their names, there is the horde of Wall Street executives. The contact book is dated for sure, replete as it is with misspellings and incorrect or superseded phone numbers, emails, and addresses. It remains something of an enigma: What was the book’s purpose? “I don’t think it means anything,” the Wall Street executive continues. “…I didn’t really know Jeffrey. He was like Boo Radley in the corner of the room. After I met him, he became Jeffrey Epstein, he had no interest in me. He knew right out of the box who the players were, the people who would stay out all night, people who had interests in extracurricular objectives, and who the hitters were. That wasn’t me.”

The Wall Street names in the book range from the highly prominent to the obscure, and, for some unknown reason, a disproportionate number of names of bankers in it worked once upon a time at Lazard, my old firm. The prominent are easy to identify, but why were their names in the book? Why would the late David Rockefeller’s name be in there? He was, of course, the textbook definition of moral rectitude before he died two years ago, at the age of 101. Also in the Epstein book are deceased financiers, such as Lord Hanson, the British industrialist; John Gutfreund, the onetime “King of Wall Street,” who presided over a major Treasury market scandal when he was the leader of Salomon Brothers; Paul Allen, the cofounder of Microsoft; Edmond Safra, a billionaire banker who perished in a fire in his apartment in Monaco in 1999; and Al Taubman, the billionaire Detroit real-estate tycoon who was caught up in a scandal involving Sotheby’s. (Taubman’s son Bobby is also in Epstein’s book).

Then there are a passel of billionaires who are very much alive. There is the multi-billionaire philanthropist and staunch conservative David Koch; Mike Bloomberg, the multi-billionaire former mayor of New York City and erstwhile presidential candidate; and there is Eddie Lampert, the billionaire hedge fund manager now presiding over the bankruptcy of Sears. There are the Forbes brothers—Steve, a onetime presidential candidate, and Chris, known as “Kip”—whose father was Malcolm Forbes and who may have at one point been billionaires. There are also the billionaires Ron Burkle, the onetime supermarket buyout impresario (and great friend of Bill Clinton), and Edgar Bronfman Jr., the spirits scion who took the family’s fortune and went Hollywood, with mixed success.