It was really exciting. After all those years of chasing bizarre and obscure radio stations with his transmitter and receiver, John was ready to see what they were saying.

Amateur radio had been like a gateway drug, and once he could receive broadcasts from far enough away John had discovered numbers stations. They were mysterious, high-frequency transmissions that repeated buzzes electronic tones, numbers, or letters, and the other amateurs John consulted with agreed that they were probably used for espionage. If a spy in the field had a special sheet called a “one-time pad” with the decryption key, which was truly random, as big or bigger than the message, used only once (and destroyed after use), and kept totally secret.

The code was literally impossible to break without knowing the key on a one-time pad.

And the envelope that John had just received in the mail had a warped and bubbled one-time pad that had been supposedly recovered from a sewer pipe.

John turned the transmitter on at the appointed time, which he had carefully researched beforehand. A metallic, artificial woman’s voice began reading phonetic letters after a brief musical tone: “Bravo, Echo, Hotel, Juliett, Kilo, Mike, Papa, Quebec, Romeo, Whiskey, Zulu.”

For each letter, John used the appropriate space on the one-time pad, and gradually a message began to emerge:

JOHN T GUNDERSON WE KNOW YOU ARE LISTENING