Wild

Twenty years ago, at the age of 26, one woman, Cheryl Strayed, set out to hike the 1,100 mile Pacific Crest Trail. It was a hike many people had made before her, but for Strayed, a recent divorcee and former heroine addict still struggling to cope with a past bereavement, it was a life-changing experience. In 2012, she published a memoir about it and saw it quickly become a bestseller. Now Jean-Marc Vallée has brought it to the screen, letting viewers see some of what Cheryl saw as she walked across the desert, through the fields and forests and up the mountains.

The humour in this film is gently underplayed so not everyone will get it, but it's more endearing as a result. Experienced hikers will shudder as they see her set off with a backpack that looks like it weighs as much as she does, packed full of completely unnecessary stuff and - as soon becomes clear - lacking some essential stuff. Although the real Cheryl had a background as an amateur runner, Reese Witherspoon's version is exhausted by the time she reaches mile three, but this will likely make it easier for the average viewer to relate. The heat clinging round the rocks and scrub is palpable; this is not a kind landscape for anybody.

Intermingled with Strayed's adventure, as in the book, are flashbacks which gradually reveal something of the life she had before. Vallée has taken a collage approach to these and the film is stronger for it. His brilliant editing (teamwork with Martin Pensa) presents a sensual picture of Strayed's past sexual exploits and drug experiences; the way she sizes up men she meets along her way, even when she says she's not looking to meet anyone, shows us that she's somebody very much in control of her desires, and the film bravely shows us her lack of regret about anything she did. Although she talks about going out into the wild to find herself, she seems more whole to begin with than most people. Only one thing really haunts her: thoughts of her mother (Laura Dern in one of the year's strongest supporting performances). Obsessing about this point of weakness, she throws herself into situations where she can find new vulnerabilities. As she repeatedly gets out of her depth one begins to suspect that her lack of preparation is deliberate - that this is an extension of past risk-taking behaviour. Danger makes her feel connected to the world.

At her best since Walk The Line, Witherspoon completely inhabits the role, bringing viewers face to face with immediacy that comes of living that way. It's sad that characters based on real women still make up the majority of really good roles for actresses, but Witherspoon lets nothing of what she is gifted with here go to waste. There's not a shred of vanity in her approach and as such she's perfectly suited to both the comedy and the tension of the piece.

If there's a weakness to the film, it's Nick Hornby's script. Though it works well enough for the bulk of the film, there are some cheesy signposting lines early on and, well, let's just say that you'll enjoy the film more if you leave just before the end, around the point where our heroine steps onto a bridge. A film whose strength lies in its immersiveness doesn't need a twee summation and we don't need to hear that Cheryl learned something today. We just need to watch, and experience, and be there with her.