The Zodiac Killer is one of the most infamous and mysterious serial killers in American history, responsible for a series of brutal murders in Northern California between 1968 and 1969, explored once again in Netflix’s new docuseries This Is the Zodiac Speaking. He claimed multiple victims and terrorized the public by sending cryptic letters and ciphers to local newspapers, taunting law enforcement with threats and demands. Despite numerous investigations and a few suspects, including Arthur Leigh Allen, the true identity of the Zodiac Killer remains unsolved.