This Is the Zodiac Speaking

Northern California, 1968. A masked killer spent fourteen months targeting couples in isolated locations — lovers' lanes, lakeside picnic spots, a quiet San Francisco street — using different weapons each time, calling in his own crimes from payphones, and then vanishing. When the killing stopped, the taunting began: fifteen authenticated letters to police and newspaper editors over five years, encrypted with ciphers that took decades to crack and two that have never been solved.

This episode opens on December 20, 1968, at a lovers' lane near Benicia, and follows every confirmed attack through October 1969. It reconstructs the letter campaign that came after — including the one-year anniversary plea to a celebrity lawyer and the final 1974 scoreboard — then walks through what two ciphers revealed when broken, and what two others still refuse to say. The back half of the episode examines the only man investigators ever formally named as a suspect, why the forensic evidence pointed away from him, and what became of the case in the fifty-five years since the last confirmed murder. As of today, no one has ever been arrested.