YOU are stranded in the North African desert with little food and water, under a lethal sun: what do you do? Probably not, as here, perform a version of the Shakespearian tragedy King Lear. Do you?

This is a powerful and affecting investigation into shifting human relationships under stress - or as Henry, a retired actor, and the character who has the inspiration for the performance puts it: "some fantastic striptease of basic human needs".

It is a relief to see the film avoid the pitfalls of the disaster movie genre, perhaps as you would expect from this the fourth film to be made according to the Dogme95 "vow of chastity". Genre plot device, along with soundtrack and other trappings of big-budget filmmaking are eschewed in favour of a stripped-down filmmaking process.

When the bus that they are travelling in runs out of petrol several hundred miles off-course (the bus's compass broke), a group of European and American tourists find refuge in an abandoned village. They catch the night dew for water, we are told, and eat old tins of carrots, left by the company that once mined this spot. Physical survival out of the way, the question becomes one of psychological survival. How to deal with the silence and emptiness of the desert? One of them plays golf. For the others, performing a play becomes a way of maintaining some sanity.

Henry (David Bradley), writes his play from memory. When Catherine (Romaine Bohringer), an attractive intellectual young French woman spurns his attempts to enrole her as the king's favourite Cordelia, he turns to the more flighty, blonde chick Gina (Jennifer Jason Leigh). In turn the others warm to his project.

Each of the characters, a dysfunctional but not wholly unattractive bunch, grapple with their demons - lust, fear, hate, violence, blindness, selfishness and vanity. There is comedy and pathos, as well as madness, as things fall apart at their core. "They grew more afraid, but they did not hold each other," a African voice-over tells us. "They filled the days with words, although they did not know what the words meant".

The voice is that of the sole inhabitant of the village, an old Namimbian sage, who sits regally under a shelter, watching the real-life drama unfold before him. He never seems to move, but his words have a simple wisdom, much like a Greek chorus.

This is such a self-contained, single location work, perfect for the limitations laid out by the Dogme95 Vow. It could almost be a play in itself, but then you would miss out on the atmospheric setting of the desert, with its undulating sand dunes and emptiness. Then there is the magnificent light, varying from the bleachy sunlight of day to the sometimes exquisite dusk glow. The filming and editing, although often handheld, does not demand much work on the audience's part, and the performances, which frequently have an improvised feel are by-and-large excellent. This a class line-up.

Without overdoing the parallel with the original tragedy, the film resonates powerfully with King Lear's existential themes long after you have left the cinema. Old Will would approve.