[Image courtesy of Wonderopolis.]

The best thing about secret codes is that they can hide in plain sight. In the past, we’ve referenced all sorts of ciphers and codes that were employed to pass secret messages across open channels.

But, as it turns out, clandestine communication isn’t the only end to which secret codes can be applied.

Recently, I stumbled upon a series of Tweets that detailed a mystery at a library involving a secret code.

[Image courtesy of Princeton.edu.]

Take it away, Georgia:

So there was a MYSTERY at the library today.

A wee old women came in and said “I’ve a question. Why does page 7 in all the books I take out have the 7 underlined in pen? It seems odd.”

“What?” I say, thinking she might be a bit off her rocker. She showed me, and they did.

I asked if she was doing it, she said she wasn’t and showed me the new book she was getting out that she hadn’t even had yet. It also had the 7 underlined! “I don’t know, maybe someone really likes page 7?” I said, assuming of course that there is a serial killer in the library.

I checked some other books. Most didn’t have it, but a lot in this genre did – they’re “wee old women” books (romances set in wartime Britain etc). Lots of underlined 7s. The woman who pointed it out shrugged and went on her way, “just thought you should know”.

[Image courtesy of MovieSteve.com.]

What could it mean? Was there a secret message spelled out somehow across the seventh page of all these books? Perhaps the seventh word? What could the message be? A warning? A threat? A great universal truth? A clue to a hidden treasure? The start of a symbol-laden journey across European with sinister forces hot on your heels?

Well, no. Calm down.

As it turns out, there wasn’t a secret message or a hunt across Europe or a threat from a diabolical library-obsessed serial killer on the loose. There was simply an elderly client with her own unique code.

Apparently, she was underlining page 7 in every book she read, in order to keep track of which books she’d already read, in case she comes across it on the shelf again.

And she’s far from the only one! Upon further research, the librarian uncovered a number of different tracking systems, many of them pre-dating the use of computers to keep library records!

Whether there’s a little star on the last page, or an F on the title page, or a page 7 underlined, each code reveals a different, dedicated reader with their own system.

When she posted this story on Twitter, other library employees and former employees piped up to share their own encounters with secret library codes that patrons employed!

I think it’s fascinating that systems like this seem to have been around as long as libraries, probably discovered (and re-discovered) periodically as different patrons and librarians alike notice them.

Better living through secret codes. Who knew?

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