Higher, Walk With Me: Wild’s protagonist leaves heroin behind on the trail.

Say you’re making a movie, and your main character is a female fuck-up. She shoots smack; she sasses her therapist. And her married status doesn’t stop her from becoming the town bicycle, so to speak, after she suffers a devastating loss. Or, as the character herself puts it: “I’m the girl who says yes instead of no.”

You need an actress who is anger personified and can pull off a motorcycle jacket and plenty of cursing. So you cast Reese Witherspoon.

Huh? Perky Witherspoon plays the damaged Cheryl Strayed in Wild, Jean-Marc Vallée’s film based on Strayed’s memoir. The gist of the story is Strayed’s decision to hike the 1,100-mile Pacific Crest Trail—solo, with zero experience—at a point in her life when everything is so broken she can think of no alternative besides handing herself over to Mother Nature to fix, phoenix-style.

With a script by Nick Hornby, Vallée (seducing the Academy for a second consecutive year after Dallas Buyers Club) approaches the material with a 127 Hours framing. So no, the film isn’t two hours of Cheryl breathing heavily, becoming filthier, and panicking over bumps in the night. Instead, her three-month journey is interrupted by memories, most prompted by something she encounters along the way. It’s a nonlinear and natural flow; Cheryl doesn’t, say, see a first-aid kit and flash back to her mother, Bobbie (Laura Dern), in the hospital.

Bobbie’s rapid death from cancer at age 45 is what started Cheryl’s spiral, with her later telling a counselor that her mother was “the love of my life.” While she was alive, however, the two engaged in glass-half-full (or is it half-empty?) bickering. Bobbie’s relentless cheer irked Cheryl (which isn’t difficult to understand, given Dern’s nearly loony performance), who questioned how her mother could sing and dance though they “had nothing.” Cheryl seemed the parent to Bobbie’s child.

Though Witherspoon overdoes the bad-girl bit in the therapy scene—maybe Vallée shouldn’t have had her chew gum and wear a leather jacket—she makes it unexpectedly easy to get past that pert face. (As far as the casting, producing the film likely boosted Witherspoon’s chances.) Early on, we see Cheryl sit near a cliff to inspect the damage to her feet, only to accidentally knock one boot down to Wile E. Coyote depths. She whips the other one and shrieks, “Fuck you, bitch!” Then she shrieks some more. It’s a wail that can come only from the deeply wounded, and you instinctively understand why this woman needed to get away from the world despite overwhelming risk.

Cheryl survives some harrowing moments, particularly among men whose intentions she has trouble judging, at least until they reveal themselves. (“Here’s to a young girl, all alone in the woods” sinks your stomach, while an offer of red licorice has never provided such a sense a relief.) Even if you can’t relate to Cheryl’s grief (losing not only her mother, but her husband through divorce), promiscuity, or drug use, her main role here—novice hiker—brings laughs as she packs way too much, swears, struggles to put up a tent, and questions her choice of trip from nearly her very first step. She’s a regular, fallible, likable human, not a walking teachable moment.

For all the emotion that spurred Strayed to take this hike and write her book, Wild isn’t drowning in tears. (At least not until near the end, when a little boy may blindside you as he does Cheryl.) Yet there’s a fear expressed in its final moments that’s universal: “I’m going to have to start living,” she writes in a journal. “And I’m nowhere near ready.” It’s an anxiety that bubbles up whenever we face a new chapter, a rite-of-passage worry that no amount of life experience will likely ever erase.

Wild opens Dec. 5 at E Street Cinema.