A crazy true story that longtime Portlanders may be familiar with has just been adapted into a film.

Leave No Trace, the story of a father-daughter pair living undetected in the woods of Portland, is playing this weekend at the Sundance Film Festival in Utah. Its plot is based on true events.

In April of 2004, according to a Spokesman Review article from the time, an Australian couple jogging through Forest Park found Frank and Ruth—a 53-year-old father and his 12-year-old daughter—living in a dugout in a remote part of the park. They'd been living there in secret for four years.

Frank and his daughter had been surviving with a small shelter, sleeping bags, a Bible, rakes, a rope swing and a tilled vegetable garden. A stack of encyclopedias had been the source of Ruth's education, reportedly.

"What was so clear was that their living conditions were unacceptable, but their relationship was a real deep love and caring for each other," the officer who found them, Michael Barkley, told the Spokesman at the time.

In 2009, Frank and Ruth's story was the inspiration for Peter Rock's novel, My Abandonment.

Rock's description of his characters provides a glimpse into their primitive survival tactics and ultimate unravelling upon being discovered.

"They inhabit an elaborate cave shelter, wash in a nearby creek, store perishables at the water's edge, use a makeshift septic system, tend a garden, even keep a library of sorts," the book's description reads. "But one small mistake allows a backcountry jogger to discover them, which derails their entire existence, ultimately provoking a deeper flight."

Last February, The Oregonian first reported that Rock's book was being adapted into a film.

And based the movie's trailer, Portland's beloved lush forest will set the stage for  most of what's likely to be a tear-inducing tale.