Under the Surface: The Dripping Pen as a Nautical Clue

In 2017, while preparing to write an article for Mike Morford’s now-defunct Zodiac Killer website, I began revisiting the Zodiac’s letters. As always, I paused at the Zodiac Killer's November 8, 1969, card—the one featuring a dripping pen on the front. It’s an odd design, with layered sections and rivets that give it a rugged, metallic feel. I had always thought it looked like part of a weathered ship. But on that day, a different word came to mind: “sub.”

Out of curiosity, I rotated the image 90 degrees counterclockwise. To my surprise, it resembled a submarine. Of course, that impression depends on which class of submarine you're imagining, but the resemblance was enough to make me look up the phrase “submarine pen.” I expected nothing of significance, but what I found was a Wikipedia entry describing a submarine pen as a fortified shelter—essentially a hardened structure or “garage” for submarines.

That caught my attention.

The Zodiac has long been speculated to have had military or naval connections, and there’s often mention of Mare Island Naval Shipyard in discussions about the Zodiac. Mare Island had a history of building submarines and so I decided to dig deeper and found a list of vessels produced there. Some of the names stood out like—Argonaut, Trigger—that felt oddly in sync with Zodiac's tone.

But what truly pushed the connection further was a quote I stumbled upon during this search:

“There is poetry in ships’ names. It can be heard in the quiet watches of the night…, when mist obscures the waterfront and foghorns call mournfully through the darkness. Out across the bay, blinking lights mark the channel down which Navy ships have sailed for hundreds of years, and bells sound a knell for those that never came back.”

This was written by Fletcher Pratt—the same Fletcher Pratt who authored Secret and Urgent, a book on cryptography that Donald Harden reportedly used during his decryption of the Zodiac’s 408 cipher. Through additional research I learned that Pratt wasn’t just a writer of nonfiction; he was also a military historian and a science fiction and fantasy author, blending fact and imagination in ways that feel oddly resonant with the Zodiac’s own method of communication.

The pen that resembles a submarine may represent more than just an abstract doodle on a card. Perhaps it has symbolic or emotional meaning for the Zodiac. What we have overlooked as incidental or decorative might, in fact, be a look inside the Zodiac's personal life. Someone who may not have been in the Navy but had an interest in certain authors, history, Naval history, ships, poetry, and science fiction.