The Unread Message: The Ciphers of the Zodiac Killer

The Zodiac Killer ciphers are among the most famous unsolved codes in the world, and after more than fifty years, two of them have still never been cracked. Between 1969 and 1970, the unidentified serial killer who called himself the Zodiac sent four coded messages to San Francisco newspapers, each a block of strange symbols mixing letters, numbers, and astrological signs. He promised that his codes would reveal his identity. The first cipher, 408 characters long, was solved in about a week by a schoolteacher and his wife at their kitchen table, but it revealed only a chilling boast, not a name. The second, known as Z340, defeated the FBI, the NSA, and the world's best codebreakers for 51 years, until an international team of three amateurs finally cracked it in December 2020, one of them working through Melbourne's COVID lockdown on the far side of the world. And two ciphers remain unsolved to this day, including a 13-character message that the Zodiac introduced with the words "My name is". In this episode of Mysteries at Bedtime, we tell the full story of the Zodiac ciphers: how the codes worked, who solved them, why the last two may be impossible to crack, and the genuinely haunting possibility that the name of a killer who was never caught has been sitting in plain sight, printed on a newspaper page, for more than half a century, in a code that no one has ever been able to read. Settle in, get comfortable, and let us tell you the story of the unread message.

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