What started as an idea back in 2000 has finally become a completed project: Bangor brothers Josh and Seth Gass have finished their first feature-length film, “The Mushing Mill,” and will premiere it at the Bangor Opera House at 5 p.m. Wednesday, Dec. 27, in a showing sponsored by River City Cinema.

The brothers Gass both now work in the film and television industries in Los Angeles (Seth is an art director for the Fox series “24”), but their film is all about Maine – from the cast members to the score, created by former Bangor resident Roy Burns.

“A lot of the people that will be coming [to the showing] are people that even in the smallest of ways contributed,” said Josh, 26. “We shot the film in Bangor and Greenville, and almost all of our early investors were from Maine. We’re really happy to share it with all of them.”

River City Cinema has had a long association with “The Mushing Mill” – the society’s artistic director, Kathy Tenga-Gonzalez, has kept in touch with the brothers over the years, since first hearing about the film in 2002.

“We heard about [the movie] and kept in touch,” she said. “One of River City’s missions is to encourage filmmaking in Maine. We like to do all we can to promote things like this.”

“The Mushing Mill” takes place in 1990 and explores the relationships among a group of boys who break into a spooky old house one summer day and must battle bullies and other obstacles to protect the treasure they find there, and restore order to their neighborhood.

It’s a labor of love for the brothers, who worked on the film in their spare time, during college and later their careers.

“We didn’t have a huge budget, so it took us a very long time to go through the post-production process. We had to pull in a lot of favors to get people to work on it for us,” said Josh Gass. “We made a lot of mistakes along the way, but we learned a lot. We wanted to get it done right.”

After Wednesday’s showing, Josh and Seth plan to start shopping the film around to festivals in hopes of someday attracting a distributor.

“We hope that people will like this one enough that they’ll want to invest in it,” said Josh, who works as a freelance editor. “We’d love to make another film. We’ve got a lot of ideas. I come home at night after work and work on my own stuff. It’s very cool and rewarding.”