Wendy And Lucy

"I'm lost".

They are the words that Wendy (Michelle Williams) writes on makeshift posters, alongside a picture of her missing dog Lucy – and they are words that apply equally to herself, and more broadly, to America's dispossessed underclass.

En route from Indiana to Alaska hoping to get work there at a salmon cannery ("they need people there," as Wendy says with resonant poignancy), the young woman breaks down in a small town in northern Oregon. With a very tight travelling budget and no safety net, Wendy makes the mistake of shoplifting a tin of dogfood for her beloved Lucy, and ends up in jail. Many hours (and a fine that she can barely afford) later, Wendy is released, and goes looking for her lost dog, even as she begins to realise that her ailing car (which is also her home) is going to have to be ditched.

Kelly Reichardt's minimalist elegy is like a road movie caught in unplanned stopover. On the one hand, the need for mobility is always at the fore, whether in the way that the film's drifter protagonist is always on the move (or at least being moved on), or in Reichardt's preference for fluid tracking shots, or even in the line that becomes Wendy's mantra: "I'm just passing through." On the other hand, there is the fact that she is stuck and going nowhere, whether in jail, in the town, or, more figuratively, in a cycle of poverty and exclusion.

There may (or may not) be hope down the road, and it is on that receding horizon of opportunities that Wendy has, of necessity, staked everything – but Reichardt places far more emphasis on the securities being left behind than on the uncertainties lying ahead, in what now seems like a melancholic look at the downward drift of a whole nation. The film was in fact shot long before the Credit Crunch, in August 2007, and was envisaged by Reichardt as a 'post-Katrina story' – but viewed today it captures perfectly the mood of the recessionary moment.

Based, like Reichardt's earlier Old Joy (2006), on a short story by Jon Raymond, Wendy And Lucy is a film about helplessness, isolation and devastating loss – and the naked impact of these themes is only enhanced by the film's simple, measured style. Here Williams is stripped of her star status with a utilitarian haircut, a shapeless hoodie, and a performance that is all the more aching for its undemonstrativeness. Of course, these elements also highlight Wendy's own increasing depersonalisation and anonymity, as she loses one by one all the conventional markers of autonomy and individuality.

Wendy is treated with insensitivity by some (like John Robinson's smug shop assistant Andy, who toes the neo-con line: "If a person can't afford dog food, they shouldn't have a dog"), and with kindness by others (most notably Walter Dalton's security guard) – but perhaps her most haunting encounter takes place late at night in a park, when a disturbed hobo (played by co-producer Larry Fessenden) looms over her sleeping bag, raving in menacing tones. Certainly he highlights Wendy's extreme vulnerability – alone, exposed and entirely at his mercy – but there is also the sense, alarming in a more subtle way, that what he is, she might herself so easily become. "They treat me like trash, like I ain't got no rights," the man mutters. "they can smell the weakness on you" - and we are reminded immediately of Wendy's predicament, and more generally of the questioning by Andy of her own rights.

Should someone in Wendy's position own a dog? It is the question on which the whole film hinges - and in supplying their own answer, viewers will end up defining themselves and their values, be they unstintingly compassionate, casually inhuman, or anywhere in between. It is why this quiet, unfussy film feels more important than a whole host of glossy blockbusters, raising urgent yet easily ignored questions about the often unforgiving economic environment of which everyone forms a part. The final credits roll, and we all inevitably move on with our lives – but you might just find yourself, like Wendy, looking back and thinking about what has been forsaken.