the late 1960s, Northern California was terrorized by an unknown murderer who called himself the “Zodiac.” Between 1968 and 1969, the killer attacked couples in secluded areas and a lone cab driver in San Francisco. After the murders, he sent taunting letters to newspapers, including cryptic ciphers, symbols, and threats—demanding they be published or he would kill again. What made the case even more chilling was the Zodiac’s obsession with control and publicity. Some of his coded messages were