This would actually be kind of cool

Sometime in the early 1980s, when I lived in Cambridge, Massachusetts, I received a postcard with a name and return address I didn’t recognize, bearing a cryptic image on the back. Every few weeks after that I received another card. There was one with holes punched in it, one with a symbol that resembled crosshairs, one with a picture of a man in sunglasses and a hooded sweatshirt, and one with a string of binary digits. The return addresses and postmarks kept changing. Assuming a friend from college was trying to get me to play some sort of puzzle game—a recreation for which I have no patience—I threw them in a drawer, a little guilty that he was going to all this trouble.

Then I received an article reciting details of the unsolved "Zodiac murders" that had unfolded in Northern California more than a decade earlier. In an episode that has since been recounted by countless journalists and Hollywood filmmakers, the killer had ambushed and slain five people. (The murderer has never been identified for certain, although numerous people have claimed to pinpoint the culprit—including a San Francisco woman who held a press conference in April declaring her father was the Zodiac killer.) He then sent letters to Bay Area newspapers threatening to kill many more unless they published a series of cryptic symbols, an act that created widespread panic. Included in the article I received were descriptions of the symbols, which sounded just like the ones on the postcards in my drawer. "Holy cow!" I said. "I’m getting mail from a mass murderer!" I called the local FBI branch, and a nice young woman with an FBI badge came to my office, picked up the collection of mail, said thank you, and left.

A week later, another agent came by with everything in a plastic envelope, gave it to me, and said, "Don’t worry, he’s harmless."

"He’s what? What do you mean, harmless?"

"Don’t you know about this guy?"

"I don’t know what you’re talking about. Do you mean the murderer?"

The agent then explained that the mail was from an amateur sleuth in California named Gareth Penn, who had been trying for some time to interest the police in the idea that I was the Zodiac killer.

Confessions of a Non-Serial Killer