A father (Viggo Mortenson) and son (Kodi Smit-McPhee) walk through the blasted, icy landscape of post-apocalyptic America on their way to the coast. On their journey, they meet other survivors – some good, some downright horrific – who test their ability to keep hold of their humanity.

What we thought:

Post-apocalyptic movies are an odd genre. Usually wedged somewhere between science-fiction and disaster flicks, they take the premise of a world gone to hell in a handbasket and layer more familiar stories on top of it – with mixed results. Sometimes you get a top-notch zombie thriller (28 Days Later) and sometimes not (the god-awful I Am Legend). You might get a great action movie (The Road Warrior) or you might get a stinker (The Postman). The Road, based on Cormac McCarthy's Pulitzer-winning novel, takes a different tack. It strips away all of these distracting plot devices to concentrate on the underlying psychological issue: when the rule of law breaks down, men behave like animals – or worse.

The plot of The Road really is that simple: a father and son need to survive long enough to reach the coast, at which point surviving may or may not become easier. On their odyssey, though, they find themselves relentlessly tested by questions of trust and goodness. The land is plagued by marauding bands of cannibals – could you shoot your 10-year-old son in the head, rather than let him fall into their hands? A thief steals to survive – can you consign him to death by stealing back from him? They are terrible, weighty questions that slowly chip away at the sense of decency and humanity cherished by Viggo Mortenson's character of The Man. As he tells his son, "I will kill anyone who touches you. Because that's my job." His only glimmer of light is the naïve trust of The Boy – a quality that The Man has to alternately try to beat out of him and nurture.

Mortenson is superb as a man who once used optimism to keep his family together – heartbreaking fragments of life with his wife, played by Charlize Theron, appear in his dreams and musings – but who now struggles to find the compassion just to feed an old man. These battles of conscience play out in every grimy line on his face. It's a mesmerising performance. His desperate co-dependence on his son is perfectly matched by Kodi Smit-McPhee, a youngster born after the apocalypse (never fully explained) who knows no other world. When they find a stash of goods and the boy witnesses his father undertake the mystifying actions of smoking a cigarette and taking a slug of Jack Daniel's, The Man says to his son, "You think I'm from another world, don't you?" The boy mutely nods – and it's true, he is.

The film is undeniably, depressingly, suffocatingly bleak – if you've seen Fernando Meirelles's adaptation of Blindness, you'll have an idea of the atmosphere of The Road. And yet throughout, essentially, there remains a spark of hope. Like when The Boy experiences a can of Coke for the first time, the film returns to the moments of innocence and rare pleasure that lighten our burden of existence and justify our humanity.

Whether these moments of relief are enough to make watching this film an enjoyable experience depends entirely on the temperament of the viewer. What is guaranteed, though, is a surprisingly faithful adaptation of a deeply powerful book, and a film full of images and exchanges that linger long after we've returned to civilisation.