It’s a beautiful, spring Wednesday evening, and I’m being chased by an unruly mob through the Seaport District.

I'm running with Holly Klose and Puja Patel, who are laying a trail, marking the ground beneath them with thick sticks of chalk as they run. And they have to keep running, because somewhere behind, that mob is following the chalk trail, getting closer by the minute. The mob has been drinking beer. They are thirsty for more beer. And the path to quenching their thirst is the very one we are laying.

Klose, Patel and the shouting hoard pursuing them are called hashers. Every week in Boston the hashers gather at a different spot somewhere in the city. While the group socializes and has a beer or three, two of them, called hares—like rabbits—will run ahead of the pack and start laying the trail that the rest will try to follow in a kind of madcap scavenger hunt through the city.

“We call ourselves a drinking club with a running problem,” Klose explained. “Every kennel every club is a little different. Ours tends to run about four or five miles, stop and have some beers along the way, and … it’s also just fun to make fools of yourselves.”

Believe it or not, there are hashers all over the world. You can find groups in pretty much any city the U.S., and there are hashes in Vietnam, Portugal, Guatemala, Nairobi. It’s kind of a bawdy, adult version of an old English children’s game, “Hounds and Hares.”

And it is, to be sure, a little childish: That’s the point. But there’s also an art to this game.

Klose and Patel spent days scouting the area, plotting the secret route they would lay out. As they run, they’re creating an experience, an adventure, using nothing but chalk, imagination, and the raw ingredients of the city itself: alleyways, bridges, train tracks.

“We know, because we scouted, that it doesn’t go through over there,” Klose said, pointing to an industrial gangway she’s marked with chalk. “But they don’t know that until they check.”

To slow the hashers down, they lay little traps, plant false trails, with Klose laying the real trail ahead and Patel dashing off to scratch chalkmarks in the wrong direction.

We finally make it, panting, to the first beer check, a secluded stop along the harbor. It’s a beautiful spring evening and the sun is just starting to set. It’s suddenly quiet. There’s nothing left to do but wait for the hashers to find us.

Joggers go by. A man pushes a trash bin. The world starts to seem, well, ordinary again. But then, in the distance,  a muffled shout—then a louder one.

“On!" the voice yelled. "On!”

The hashers pour in, cheerfully whooping; a couple jump right into the harbor. While the group takes a beery breather, Klose and Patel slip quietly away again with their chalk, laying the route home (another bar) where the hashers will, in their own way, sing the praises of the hares whose simple trail brought everyone here, together, happy: “That trail really blew, so why not drink a brew? Drink it down, down …”

Tomorrow, the rowdy hashers will be back at their jobs. They’ll cross streets at the crosswalks, and return emails, and return to being, well, normal people. But waiting for them next week, laid out in exuberant chalk, will be a fresh new trail—another evening of adventure.