NEW YORK, NY.- For certain corners of the internet, a 1976 paperback edition of Madeleine L’Engle’s novel “A Wrinkle in Time” has been the source of an enduring mystery: Who was the artist behind its spooky, glowing-green cover art?

After a few hours of research, podcast host Amory Sivertson thought she had found the answer. She had emailed a gallery to ask if an artist it represented had made the cover and a worker said yes.

She was wrong: A day later, the gallery worker apologized for the miscommunication. It would be two months, hundreds of emails and a number of awkward cold calls before she actually found the correct name.

The mystery cover art shows a strapping centaur with delicate wings flying above a menacing green face with bright red eyes. Craggy mountains and fluffy dark clouds surround the haunting figures. The website Book Riot called the art “nightmare fuel.” The artist’s name isn’t mentioned anywhere in the book.

Sivertson thought that finding the artist’s name and giving the person credit were important for a work that is “on people’s bookshelves and in their hearts and in their memories.”

“This is one of the pieces that outlives him,” Sivertson said of the cover. “It’s just — you have to know. We have to find out who is behind it.”

The mystery reached Sivertson because she is the co-host and senior producer of the podcast “Endless Thread,” which sometimes delves into mysteries. On the show — produced by Boston’s NPR station WBUR — Sivertson and her co-host, Ben Brock Johnson, find explanations for quandaries such as Geedis, a warthog-like character that dazzled the internet, and a pile of plates dumped in the woods in Pennsylvania.

For the book art mystery, the podcast picked up where S. Elizabeth, who writes the blog Unquiet Things, had left off.

Elizabeth said she had first developed an “idle curiosity” about the artist behind the “Wrinkle in Time” cover art in 2019. In 2021 and 2022, her curiosity increased as she worked on her latest book, “The Art of Fantasy,” a compendium that comes out on Thursday.

In May, she described her search for the artist in a blog post, hoping it would generate new leads. She said that she had contacted people online who were connected to the novel, the fantasy art world and L’Engle. Elizabeth reached out to L’Engle’s granddaughter on the social media platform X to ask if she knew who created the cover, but the account responded with a shrug emoji.

Elizabeth posted about the search on Reddit, and a commenter there said the mystery would be a good fit for “Endless Thread,” so Elizabeth shared her request for help on the podcast’s subreddit.

Elizabeth didn’t have an especially deep connection to the book. When she first started looking for the cover artist, her primary memory of the novel was that the plot involved a liverwurst sandwich — “I’m a foodie,” she said — but she cares deeply about artists getting their due.

The search for an answer resonated online with many, who sent Elizabeth guesses about the artist’s identity and tips for her search.

“I think realizing that the artist was not so easily found — that just lit a fire under a lot of folks, because this book was so formative to so many people,” Elizabeth said.

People had guesses (spoiler: Some were correct), but Sivertson’s hundreds of calls ultimately led to an answer. “I really was sustained by people who would write back and say, ‘I have a few ideas, let me make a few calls,’” she said.

Sivertson said these calls were “an industry coming back together,” with people who worked in publishing and illustration in the 1970s speaking with each other for the first time in decades.

In late June, she was given the correct name: Richard Bober. Bober died last year, but Sivertson was able to speak with his relatives in early July, and she said they found proof that he had made the cover art.

Elizabeth said that she wanted to burst into tears when the mystery was solved because even though Sivertson was tenacious, finding the answer had seemed like a long shot.

Elizabeth had actually seen a work by Bober before, “Lady Vampire,” which she said depicts a vampire girl who looks “like a snotty, mean girl,” with a dog looking at her adoringly. “At the time I thought, ‘This artist is so cool,’” Elizabeth recalled.

This cover art mystery appears to be solved, but Elizabeth has a long list of queries she would still like answers to, including who made a cover for the next book in L’Engle’s series: “A Wind in the Door.” Each year on social media, Elizabeth also posts a photo of a topless woman in an enormous headdress taken during what appears to be the 1920s, hoping someone will know who it is.

“Everyone has tons of guesses,” she said. “And some people are like, ‘Definitively, yes, this is that person.’ But show me the proof of it.”

This article originally appeared in The New York Times.