Northern California, 1969. December 20th, 1968. Two teenagers parked on a remote road near Vallejo, California. They had only known each other for 2 weeks. By the time a motorist [music] found them, both were dead. The police had no motive, no suspect, no answers. They called it the work of a madman and moved on. Then it happened again. July 4th, 1969. A couple in a parked car. Same remote setting, same silence. This time, one survived. Less than 1 hour later, the killer called the Vallejo Police Department himself. "I also killed those kids last year." Then, three letters arrived simultaneously at three Bay Area newspapers. Same day, same handwriting, same demand. Each letter contained 1/3 of a 408-symbol cipher. [music] The writer said the code contained his identity. He demanded it be printed on the front page, or he would kill again. 8 days later, a high school teacher and his wife cracked the code. "I like killing people because it is so much fun. It is more fun than killing wild game in the forest because man is the most dangerous animal of all." October 11th, 1969. A man hailed a taxi in downtown San Francisco. He asked to be driven to Presidio Heights. When the cab stopped, he shot the driver and climbed into the front seat to wipe away fingerprints. Three teenagers across the street saw [music] everything. Two officers arrived in under 3 minutes. They spotted a man walking alone and asked if he had seen anything suspicious. The man said yes. He'd seen someone with a gun heading east. The officers drove away. The man they spoke to was the Zodiac. He later wrote a letter confirming it, laughing that the cops [music] pulled a goof and let him walk right into the park. In 2020, [music] a team of amateur code breakers finally cracked his most famous 340-symbol cipher. After 51 years of silence, it read, "I hope you are having lots of fun in trying to catch me. I now have enough slaves to work for me in paradise." He was never caught. One cipher still hasn't been solved. The one that begins with the chilling words, "My name is Whoever he was, he's either dead or he's been among us this whole time.