FAIRFIELD — A Horcrux is hidden in Malfoy Manor. Just through a nearby door, teen librarian Marissa Bucci explains to a group of seven boys and a girl, all ages nine to 12.

“You mean a part of Voldemort’s soul?” one shouts in excitement.

Bucci recites an intercepted letter from Bellatrix Lestrange to Lucius Malfoy and then gets one question from the group of kids in response: “Is Dobby going to be involved?”

Fairfield Public Library’s “Escape from Malfoy Manor,” a Harry Potter-themed, locked-room mystery kicked off Wednesday and ran through Saturday night.

“It’s an unforgettable experience for the teens and the adults, too,” head teen librarian Nicole Scherer said.

For the game, librarians used “puzzle-able” items that happened to be part of the library’s Memorial and Jennings Rooms, collected old, antique or broken props from their own things and the library’s storage, and created clues from a potion-mixing spread to a birth certificate, Scherer said.

During the game, players used potion mixes, UV lights, locks, hints and clues to find a final item, the Horcrux, to end the game - hopefully working as a team to beat other groups’ times. As some kids searched carefully through bookshelves, others ran excitedly from room to room, yelling about clues and codes until papers and keys were strewn across tables and areas of the floor.

“It was fun and challenging,” said Jack Harrington, part of Wednesday’s tween group, “Team Squeaky Rat.”

Scherer said the library chose a Harry Potter theme, “Escape from Malfoy Manor,” to coordinate with the release of “Harry Potter and the Cursed Child” Saturday night. The library hosted three sessions of the locked room mysteries each day on Wednesday and Thursday. Friday got two sessions, while the four on Saturday culminated with the library’s release party for the new Harry Potter story. The Fairfield Bookstore jumped on board to co-host the release party, which will feature Saugatuck Sweets ice cream.

The game had tween, teen and adult sessions, broken down by ages nine to 12, 13 to 18 and 18 and up, respectively.

The game’s test took staff 48 minutes and 13 seconds on Wednesday morning, which the tween session beat with a time of 46 minutes and 20 seconds.

Bucci, who designed the “Escape from Malfoy Manor” game, said, while the mystery and clues remain exactly the same for kid, teen and adult sessions, each age group approaches it with different thought processes. Adults often overthink clues, she said, while children or young teens are more likely to take them at face value.

Bucci and Scherer facilitated the sessions in the locked room with players. During the “tween” session, they more actively guided kids to put their clues together, while they did not help beyond the three allowed hints in the teen and adult sessions.

Scherer said they also see a difference with video game players, who tend to more naturally gravitated to trying clues repeatedly until they work, which was often helpful in the game.

Fairfield Public Library was among the first libraries in the country to run locked-room mysteries, a recent commercial trend, Scherer said. The library hosted its first series in February with a pirate and treasure-hunting theme, titled “Escape the Attic.”

After the February series, Scherer wrote a manual for libraries to stage locked-room mysteries, which she said has been shared with hundreds in the library community, as well as outside the United States.

Pat Sheary, adult programming and book groups librarian at the Darien Library, went to the adult session on Wednesday night. Though had never read the Harry Potter series, Sheary had done a commercial locked-room mystery before and said she found the library’s version even more fun.

“I thought that it was incredibly clever,” she said. “It was interactive enough that if you were frustrated, you were never bored.”

Mallory Arents, a Stamford resident who was also part of Wednesday night’s adult team, said she liked seeing how different people’s skills ended up coming together.

“I’ve been to a fair amount of escape rooms,” she said. “I love the trend. I think it’s really fun to creatively problem solve and work together as a team.”

As a Harry Potter fan, Arents said she loved the Malfoy Manor theme and found the feeling of the room gave a genuine Harry Potter vibe.

A Harry Potter fan herself, Bucci was excited to work on the theme that she “grew up with,” but, she said, is still a part of new generations’ lives.

Up to 10 people could sign up for each locked room mystery. Before the first session on Wednesday, all spots had been filled.

LWeiss@hearstmediact.com; @LauraEWeiss16