Dear Robin,

You make your mark early, as Wild opens on a craggy California slope. A young woman, her skin burnished by the sun and streaked with dirt, sits beside her oversized backpack . She pulls off her boots and socks to reveal blistered, bloody feet, skin rubbed raw, toenails barely attached. What happens next informs the tone of the film. For anyone who thought they were coming to see a glamourously windblown actress trekking across a softly focused vista, the first scene issues a harsh warning.

This ain’t gonna be pretty.

In the four years since the death of her mother, Cheryl Strayed goes from promising college student to a heroin and sex addict who effectively drives away those closest to her. In the summer of 1995, she sets out to hike 1100 miles of the Pacific Crest Trail, which stretches across several mountain ranges from Mexico to Canada. A novice hiker alone on the PCT, Cheryl will encounter physical and emotional obstacles unlike anything she has ever faced.

This isn’t the first time you’ve had to ugly up an A-list actor, nor is this the first time you’ve worked with Wild’s Canadian director, Jean-Marc Vallée. You won an Oscar for convincing audiences that Matthew McConnaughey and Jared Leto were wasting away from AIDS in Dallas Buyer’s Club. This isn’t even the first time you worked on a movie about someone walking alone in the wilderness. On Into The Wild you made Emile Hirsch’s Christopher McCandless’ malnutrition seem painfully real. The comparisons between Into The Wild and Wild are inevitable and not altogether unwarranted. But the idealistic McCandless was trying to find himself. Cheryl just wants to be lost.

What brings Cheryl to the PCT isn’t initially clear. Even she isn’t entirely sure why she’s there. The trail isn’t a metaphor for her life. It’s not redemption. But for almost a hundred days it is her closest friend and fiercest enemy. Cinematographer Yves Bélanger films it as such, equal parts stunning and humbling, serene and relentless. When Cheryl dreads each monotonous footstep, so do we. When she takes a moment to appreciate the majesty of the Sierras, we do too.

Cheryl’s past haunts her throughout her journey. Vallée uses razor-sharp cuts as flashbacks - Cheryl having sex, injecting heroin, fighting with a man - which eventually become whole scenes as she gets further into the trail. He saves the tenderness for the flashbacks of Cheryl watching her mother singing and dancing, or driving her and her brother away from their abusive father. One is a set of memories Cheryl hopes to exorcise, the other she is desperate to hold onto.

Your job was to believably transition Cheryl from college kid to junkie to weary traveller, and luckily Reese Witherspoon was your canvas. Witherspoon (who also produced) carries this film like her “Monster” – the enormous backpack Cheryl hauls across the backcountry. This is the kind of role that screams “Oscar bait!” but thankfully Reese’s performance never does. Though Cheryl was 26 when she hiked the PCT, Witherspoon delivers a cynical vulnerability that perhaps younger actresses might not have done as convincingly. Witherspoon’s Cheryl is the kind of complicated female lead we rarely see onscreen; a frustrating and reckless mess with nothing to lose. She is not easy to root for.

Vallée is careful enough to maintain the film’s vast scope without sacrificing intimacy, and smart enough to trust that an actor of Witherspoon’s talent doesn’t need much accoutrement. He uses the Simon & Garfunkel song “El Condor Paso” as a powerful yet unobtrusive leitmotif, its lyrics “If I could” perfectly echo Cheryl’s inner monologue. She could quit, she could keep going. She - and the audience - is never quite sure what she will do.

Through you, Cheryl’s face and body tell her story. Dark under-eye circles, dried blood and fading bruises fill in the blanks that Nick Hornby’s mercifully underwritten script omits. The patches of inflamed skin on Cheryl’s back and hips, rubbed raw from the weight of Monster, scab and toughen as she adjusts to carrying her burden. Facing demons and making amends is painful and it isn’t pretty, but when stripped to the bone, there’s beauty to be found in the fight.