The identity of the serial murderer known as the Zodiac Killer has been confounding investigators for over 50 years. An unlikely and unconventional character may have finally cracked America's most famous cold case by questioning if the reason the killer has never been caught, is because he never existed in the first place. The Zodiac, who coined the name in a series of taunting letters and cards that he mailed to regional newspapers, operated in Northern California in the late 1960s. Some of the letters included cryptograms, or ciphers, in which the killer claimed that he was collecting his victims as slaves for the afterlife.