All through Wild, the powerful story of a woman's trek across Western wilderness, and across a wilderness of hurt and loss, there are shots that place Reese Witherspoon alone and tiny in vast swaths of desert, mountain, and woods. Lugging a backpack practically as big as she is, Witherspoon - as best-selling memoirist Cheryl Strayed, who hiked 1,100 miles of the Pacific Crest Trail, from the Mojave to the Cascades - is a fragile figure in a beautiful, unforgiving landscape.

A complete hiking novice, Strayed purchased the equipment she thought she'd need (a lot of it she didn't, and stuff she did need she didn't get), some maps and books (one on working a compass), and a sketchbook to use as a journal, and set out on her three-month-long march. Blistered, bloodied feet were a sure thing; self-discovery, less so.

In the end, Strayed got both.

Wild has been directed by Jean-Marc Vallée, the French Canadian who steered Matthew McConaughey through his Oscar-winning performance in Dallas Buyers Club. The screenplay, deft and nuggety, comes from Nick Hornby, the About a Boy writer whose affinity for female-driven stories resulted in the pitch-perfect adaptation of Lynn Barber's '60s coming-of-age memoir, An Education. Add Witherspoon's wholly committed, wholly convincing portrayal, and you have a formidable package.

That's the (slight) problem. It feels kind of packaged, from Strayed's poetic musings to the flashbacks that rumble through her head and onto the screen: the junkie years, the cheap sex years, the crappy waitress jobs, the bum marriage. Something about the way the film has been assembled doesn't feel altogether organic.

I kept thinking of Into the Wild, Sean Penn's film about Christopher McCandless and his ultimately tragic ramble across the West. The 2007 release similarly tracked a restless soul seeking truths, meeting people along the way - but always convinced that solitude was required. Into the Wild resonated in deeper, darker ways. When Strayed looks up and sees a fox gazing back at her in the clearing, it's a kind of magical, mysterious moment - yet Vallée seems unsure how to handle such mysteries.

Wild is still a moving (literally and figuratively) experience, a road movie where the road is a trail that sometimes disappears into the trees, or takes a turn onto a jagged precipice. Communing with nature as a means to find our humanity, our spirituality, is the stuff of Thoreau, of Emerson, of Whitman ("Give me solitude/give me Nature/give me again, O Nature, your primal sanities!"). And communing with the memories of those we loved, and those who shaped us, good and bad, is key to serious self-reflection.

The person who loomed largest in Strayed's life was her mother, Bobbi. Laura Dern, in a series of wheeling flashbacks, plays the woman who endured an alcoholic and abusive husband to emerge with a hard-won but wondrous worldview. "If there's one thing I can teach you," she says to her daughter in one of their late-night kitchen talks, "it's how to find your best self."

That is why Strayed is clomping across some Oregon ridge in Wild: She is determined to find her best self. It's worth joining her.

Wild *** (Out of four stars)

Directed by Jean-Marc Vallée. With Reese Witherspoon, Laura Dern, Gaby Hoffman, Michiel Huisman. Distributed by Fox Searchlight.

Running time: 1 hour, 55 mins.

Parent's guide: R (sex, nudity, profanity, drugs, adult themes).

Playing at: Ritz Five and Carmike at Ritz Center/NJ.EndText