After 35 years, the secretive CIA sculpture finally gave up its mystery, thanks to a novelist, a playwright, and some misplaced documents. But the chase to decode continues.

Jim Sanborn couldn’t believe it. He was weeks away from auctioning off the answer to Kryptos, the sculpture he created for the CIA that had defied solution for 35 years. As always, wannabe solvers kept on paying him a $50 fee to offer their guesses to the remaining unsolved portion of the 1,800-character encrypted message, known as K4—wrong without exception. Then, on September 3, he opened an email from the latest applicant, Jarett Kobek, which started, “I believe the text of K4 is as follows …” He’d seen words like this thousands of times before. But this time, the text was correct.

“I was in shock,” Sanborn tells me. “Real serious shock.” The timing was awful. Sanborn, who turns 80 this year, saw the auction as a way for someone to continue his work of vetting potential solutions while maintaining the mystery of Kryptos. He’d also been looking forward to getting compensated for his work. What came next was even more shattering. He quickly got on the phone with Kobek and his friend Richard Byrne, who gobsmacked him by reporting they did not find the solution by codebreaking. Instead, Kobek had learned from the auction notice that some Kryptos materials were held at the Smithsonian’s Archives of American Art in Washington, DC. Kobek, a California novelist (one of his books is called I Hate the Internet), got his friend, the playwright and journalist Byrne, to photograph some of the holdings. To Kobek’s astonishment, two of the images contained a 97-character passage with words that Sanborn had previously dropped as clues. He was staring at words that CIA and NSA codebreakers, along with countless academics and hobbyists, had sought for decades.

The secret of Kryptos was out of the artist’s hands, in the most humiliating way imaginable—Sanborn himself had mistakenly submitted it in readable form to the museum. For 35 years the Kryptos plaintext had been a summit that none had reached. Suddenly some had attained it—not by climbing to the peak but by hitching a ride to the top. Sanborn’s grand vision for a piece of art that illuminated the idea of secrecy itself was imperiled—as was the auction. Now he had to figure out what to do about it.