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.

Ever since artist James Sanborn unveiled Kryptos, an outdoor sculpture that sits at CIA headquarters, amateur and professional cryptanalysts have been feverishly attempting to crack the code hidden in its nearly 1800-character message. While they have decoded 3 of the 4 panels of ciphertext in the S-shaped copper artwork, the final panel, known as K4, still defies solution. Only one human being on Earth knows the message of K4: Sanborn. But soon someone else will join the club. Sanborn is putting the answer up for sale.

For 35 years, amateur and professional cryptographers have tried to crack the code on Kryptos, a majestic sculpture that sits behind CIA headquarters in Langley, Virginia. In the 1990s, the CIA, NSA, and a Rand Corporation computer scientist independently came up with translations for three of the sculpture's four panels of scrambled letters. But the final segment, known as K4, was encoded with knottier techniques and remains unsolved. This failure has only deepened the obsession of thousands of would-be cryptanalysts. When one of them thinks they have an answer, they write to Jim Sanborn for confirmation.

Presbyterian reverend Thomas Bayes had no reason to suspect he'd make any lasting contribution to humankind. Born in England at the beginning of the 18th century, Bayes was a quiet and questioning man. He published only two works in his lifetime. In 1731, he wrote a defense of God's--and the British monarchy's--"divine benevolence," and in 1736, an anonymous defense of the logic of Isaac Newton's calculus. Yet an argument he wrote before his death in 1761 would shape the course of history.

Presbyterian reverend Thomas Bayes had no reason to suspect he'd make any lasting contribution to humankind. Born in England at the beginning of the 18th century, Bayes was a quiet and questioning man. He published only two works in his lifetime. In 1731, he wrote a defense of God's--and the British monarchy's--"divine benevolence," and in 1736, an anonymous defense of the logic of Isaac Newton's calculus. Yet an argument he wrote before his death in 1761 would shape the course of history.