Thinking out loud, here, but I was watching one of the later episodes of DARK SHADOWS, wherein Quentin Collins, played by the excellent David Selby, was falsely accused of practicing witchcraft. The REAL warlock at the time was framing him, seeking revenge on Quentin because one of Quentin’s ancestors had sentenced the warlock to death 150 years earlier. As part of the frame-up, the warlock, after murdering people known to be Quentin’s enemies, would leave a sign at the murder scene, a “symbol of the devil” that matched a ring Quentin always wore. The ring was an X partially enclosed in a circle. Then it hit me: this symbol is basically the sign the Zodiac killer of California would use to sign his taunting letters to police and the newspapers.
Take a look. The symbol on the left is Zodiac’s crosshairs symbol. The one on the right is the “devil sign.” It’s the same symbol, just tilted a little. Now it isn’t a terribly complex symbol, so there’s no reason to presume that two different people couldn’t have come up with it. But the Zodiac murders were in the news at the exact same time as this storyline was airing. Coincidence?