When the fourth-billed character in a movie’s cast is “Jack the Rapist,” it’s a pretty safe bet it’s not a comedy.

“No, that’s not a good sign!” says West Palm Beach’s Keri Lurtz, the director and star of Lost Angels: City of Dreams, a most cautionary of cautionary tales about three friends who move to Hollywood seeking fame and fortune, but find drugs, desperation, rejection and other stark realities that lead to bad decisions. Incredibly bad decisions.

Lost Angels, which premieres Saturday at Lake Park’s funky Mos’Art Theatre, is the first feature-length film for Lurtz, whose short Unconditional was an entry at the Cannes Film Festival.

Lurtz, a graduate of the Palm Beach Film School and Georgia State University, says that she and her character, Keri, both share a “Beaver Cleaver kind of Christian family background,” but not the sad slide into seediness that Keri finds herself on. “As an actor, I almost wish her life had been more eventful. That gives you so much to come out of.”

The movie was filmed both locally and in Los Angeles — check the cheery early scenes where pals Samantha (Lurtz), Nick (Christopher Swank) and Amy (Jacqueline Nicole) happily stroll Hollywood Boulevard, gazing at the stars dedicated to various celebrities, and imagine being among them. But the cheeriness doesn’t last.

Lurtz says she, director of photography Chris Alonzo, and costar and cameraman Swank went to L.A. intending to make a documentary. They had actually begun filming, when Lurtz realized it needed to be a feature.

Lurtz started writing the fictional story, “staying up every night” to tell of a dark year in the lives of Keri, who quickly gets an agent and just as quickly becomes hooked on drugs, anonymous sex and vodka-based breakfasts; Nick, whose gambling and dependence on “happy pills” sees him involved with some unsavory people; and Amy, who deals with body image issues by locking herself in her closet and eating everything in sight. Again, not a comedy.

The bi-coastal filming allowed Lurtz to do the requisite Los Angeles scenes to “get the element” of what that dream-offering city is all about, but to film interiors and other scenes in the supportive climate of Palm Beach County, including shots on West Palm Beach’s Clematis Street, the offices of Comet Electric, owned by her husband, Pete, and some Lake Worth rental properties Pete’s family owns.

“It’s hard to make a film out there. Here, people are so willing to help. They’re like ‘Yeah, yeah, come on!’ ” she says. “In L.A., they’re so used to it. Everybody’s making a film out there.”

Most everyone involved with Lost Angels is from Palm Beach County, with a few from Boston. An exception is actor David Fine, who plays the aforementioned Jack the Rapist in a “very intense scene. He’s only in one scene, but he’s simply brilliant,” she says.

She’s right — Fine’s short, shocking appearance in Lost Angels is so harrowing that it’s hard to get out of your head. It also makes you want to talk anyone you know out of ever moving to Los Angeles.

“Those are the reasons I became a filmmaker,” Lurtz says. “I want to make something that stays with ’em. That’s what I aspire to.”