An introduction to a worldwide clue game.

Dorrie McQuaid, 16, walks along a hiking trail on St. John, an island in the U.S. Virgin Islands where her family is on vacation. She asks her mom to give her the next clue.

Looking carefully at the piece of paper in her hand, her mother reads out loud: “Shiver me timbers and pieces of eight, continue the trail and speed up the rate! Pass the mammee apple tree on your right, get to the high ground and keep the cacao tree in sight.”

“What’s a mammee apple tree?” Dorrie wonders out loud, before spotting a small sign that identifies it. After a few minutes more they’re in front of yet another tree and reading the last of the directions: “Keep your back to the tree and take four paces off the trail.”

After taking four steps, Dorrie looks down at a pile of stones. Digging in carefully, she calls out, “There it is!” It is a plastic box, carefully wrapped in plastic bags to keep rain and bugs out.

The McQuaids are letterboxing, a fun outdoor activity that sends people peering into all kinds of places in search of letterboxes. “Letterbox” is the term used for a mail box in England. Modern letterboxing probably has roots in the 1850s, when an English man left cards in a bottle with a note inviting others to do the same. Pretty soon people began leaving messages or letters for other folks passing by to find.

Modern letterboxes are plastic boxes instead of a bottle. Here’s how it works: Someone hides a box, maybe under a log in the forest or tucked into a crack in an old stone wall. Inside the box, the hider places a rubber stamp and a notebook. Letterboxers post clues about how to find the box on websites like www.letterboxing.org/kids.

When you are ready to go letterboxing, have an adult go online and search for boxes by location—in your neighborhood or home town, or in a place you are going to visit. The boxes are all across the U.S. and in many other countries.

As you head out to find the letterbox, take along the clues you printed out from the Internet, a pen or pencil, a notebook, and a rubber stamp. Don’t forget the usual hiking supplies: water, bug spray, and sunscreen!

When you find a box, open the notebook you find inside. Dorrie says it is fun to see who has been there before you and where they live. (Remember to be secretive if other people are nearby; if they don’t know about letterboxing, they might take the box away).

Write your name, hometown, the date, and a short note in the log book. Don’t forget to make your mark with your own rubber stamp. (Look for a library book that explains how to design and make your own stamp!)

Then take the special stamp from inside the box and make a print in your own notebook. Collecting as many stamps in your notebook as possible is a big part of the fun. Then wrap the box up carefully and return it to its hiding place for the next letterboxer to find.

Dorrie, who found another box on St. John hidden in an old stone wall, says, “I would definitely do it again. I’m a big mystery solver—I love reading mysteries and solving problems. Letterboxing is—and it’s not like your basic tourist thing. I always like the chance to do something different!”