The human body is a wondrous piece of engineering.
Its strength doesn't come from the muscles and bones, but from the heart and brain: the motors which drive ordinary men and women to achieve superhuman feats of endurance in the most unimaginable circumstances.
One such person is Aron Ralston, an avid mountain climber who made headlines in the summer of 2003 when he became trapped in the Blue John Canyon in Utah, his arm pinned against the wall of the canyon by a heavy boulder.
After five days alone, with all hope seemingly lost and his strength evaporating in the sweltering heat, Ralston elected to amputate his trapped arm with a penknife in the hope he could go for help before losing too much blood.
Director Danny Boyle and screenwriter Simon Beaufoy, who both won Academy Awards for Slumdog Millionaire, reunite for this electrifying adaptation of Ralston's memoir, Between A Rock And A Hard Place, which reveals the internal monologue of a man who fully expected to die in the baking earth.
Boyle opens in hyperkinetic fashion with split screens and insistent music courtesy of composer AR Rahman – another Slumdog collaborator – to introduce Aron (James Franco) as he prepares for a hiking trip.
After a frenetic couple of hours on a mountain bike, Aron continues on foot and meets Megan (Amber Tamblyn) and Kristi (Kate Mara), who are lost.
The trio flirt and enjoy a dip in a subterranean lagoon.
Aron continues alone and as he attempts to traverse Blue John Canyon, the rocks give way, sending him plummeting to the bottom.
127 Hours is brilliantly realised and Boyle employs a mosaic of flashbacks, memories and dreams to achieve the seemingly impossible feat of bringing energy and movement to a film that is set, almost entirely, in one location.
The Oscar-winning director plunges us head first into Aron's nightmare, including a stomach-churning scene of the stricken man drinking his own urine shot from the point of view of the warm, yellow liquid glugging into his mouth.
Boyle also allows his camera inside the climber's battered body.
When the knife first sinks into Aron's arm, we snap to an x-ray vision of the dull blade scraping against bone.
It's a visual tour-de-force, complemented by Franco's fearless performance, that holds us spellbound, not least in the gory and bloody final scenes when Aron lops off his arm, bit by bit.
We witness tendons being severed through our fingers but cannot look away, willing him on with every fibre of our being.
The real Aron and his wife appear briefly over the end credits to confirm that life didn't just go on after Blue John Canyon – it got better.