With a faint slam, the door closes behind Rachel Larson.

The St. Paul woman inches forward as her eyes adjust to the dark. Slowly, she can make out her friends, then some of the details of the eerie room: a chessboard, a toy rifle, a large crate.

She hears the door lock and turns to see a man in black-rimmed glasses standing guard at the door. He holds a small timer.

“Did we already start?” she asks. The man doesn’t answer.

Larson and her friends are trapped.

And that’s exactly what they signed up for.

Each player has paid $25 ($26.87 with the service fee) to be imprisoned for an hour in Minneapolis’ first Riddle Room.

In this live-action game, titled “Escape From the Bunker,” players have 60 minutes to find clues scattered around the black-lit room and solve a series of riddles that will lead them to the key — and freedom.

“It’s this new thing that’s sprouting up around America, and I thought it sounded like too much fun to not do,” said Art Allen, the game’s organizer. “You are throwing yourself into a real-life video game that’s unlike anything.”

• • •

Larson heads straight for the bookcase and starts to sift quickly through the piles of books as the other players disperse around the cavernous room.

Megan Lotz, from Mounds View, searches the empty soda cans on the floor. Tom Kuehn, from Anoka, plays a record player on the other side of the room as his wife, Alia, starts to piece together a broken puzzle.

Although they’re moving quickly, the players are focused, calm and crafty.

They pepper the man in the black-rimmed glasses, their “host,” with questions. He says nothing.

• • •

Alex Davy knows all the clues that lead to the players’ freedom.

In fact, he created them.

Davy, one of the designers, also is a professional game-maker in the Twin Cities. At Allen’s request, Davy and some co-workers designed the entire escape room, including the puzzles and the décor. While Davy has had plenty of experience designing board games, he had never designed a living puzzle.

“A board game tells you exactly what’s going on,” Davy said. “For Riddle Room, everything in the room may or may not be part of the game. The board is not defined. The space is not defined.”

That made creating the riddles a challenge. Davy started by collected items that matched the room’s dilapidated interior — a toy Kalashnikov gun, several Soviet-era ammo boxes — and a theme emerged: “Escape From the Bunker.”

Escape rooms started in Japan about seven years ago and have since popped up in cities across the world, from Budapest and Paris to San Francisco. The real-life rooms were inspired by puzzle-solving animated video games from the 1970s and ’80s. (A more recent Web browser game, “Crimson Room,” is the closest relative to escape rooms.)

Allen, the man behind the Beard-Off (a local facial hair competition) and Pundamonium (a slam-style pun contest) opened his Riddle Room in northeast Minneapolis in May. Since then, it has had more than 150 players.

• • •

By now, the players in the Riddle Room are frantic. They know that time is running out, but one riddle remains: They have to crack the code on the last lock of the large crate.

The host hovers nearby, his eyes fixed on his timer.

The players shout various combinations to Larson as she spins the lock again and again. The frustration is mounting when Larson hears a click. “I got it!” she calls.

Everyone gathers around while she opens the lock. Two other players lift the lid. Inside is their final hurdle: a grenade.

A note attached to the grenade reads: “Pull pin to win.”

• • •

The players fumble for the grenade. It lands in Mark Larson’s hands.

Someone asks the host jokingly if the grenade is live. He doesn’t answer.

Mark Larson pulls the pin.

Finally, the host lets out a laugh and speaks his first words of the evening: “Congratulations, you found the only way out of the bunker.”

He flips the light switch.

And then he unlocks the door.