There are amazing feats, and then there are jaw-dropping, once-in-a-lifetime accomplishments that confirm mankind's remarkable physical and imaginative potential. Philippe Petit can lay claim to having pulled off one of the latter, as in the summer of 1974, the French tightrope walker did something no one had ever done before or will ever do again: he navigated, on foot, a single wire stretched between the World Trade Center's two towers.

As a kid, Petit was an incorrigible climber, and upon seeing a newspaper article that included a diagram of the as-yet-uncompleted Twin Towers, he immediately told himself that one day, he would cross the gulf between the enormous skyscrapers. That he had no formal wirewalk training and had never been to the United States didn't matter, nor did the nightmarish logistical hurdles that would obviously stand in his way. A dream was born, or rather something of an audacious obsession, leading him to hone his craft first through intense training sessions, then by traversing wires attached to the peaks of Notre Dame and Australia's Sydney Harbour Bridge, and finally by concocting an elaborate plot to infiltrate the still-under-construction WTC and pull off his unparalleled deed.

Despite the fact that Petit is the first interviewee featured, thereby confirming that he didn't perish while trying to carry out his chosen task, James Marsh's documentary Man on Wire generates an amazing amount of tension from its subject's story. Part of this is attributable to the director's taut, tantalizing narrative structure, in which Petit's endeavor to reach the WTC roof is interspersed with his life story and details about the illegal scheme's preparation, thereby maintaining some doubt about whether Petit was able to avoid detection long enough to fasten, and get himself onto, a wire.

But more fundamentally, Marsh's film rattles one's nerves simply via the regular sight of Petit suspended over immense chasms, appearing, from a distance, like he's literally floating in air. There's a supernatural beauty to these stark images - most coming courtesy of archival photos and film footage taken by Petit and his accomplices, which put the occasional dramatic recreations to shame - and they lend the proceedings an almost quasi-religious atmosphere, as if what we're watching is the story of a man attempting to do something divine.

Upon completing his walk, replete with trademark tricks such as lying down on the wire, Petit was asked by New York reporters why he had done it. The question, then as now, struck Petit as baffling, largely because it was beside the point. To do something beyond compare was reason enough ("There is no why" he exclaims), and Man on Wire's centerpiece imagery ably backs up his contention. Yet the film's climax is no more thrilling than its preceding heist flick-esque saga involving Petit's two motley crews made up of Americans and Europeans, one in each tower, conspiring to gain access to and ascend the buildings (by posing as construction workers and businessmen) while evading patrolling security guards.

Between Petit and a cohort having to hide for hours underneath a tarp to elude a nearby watchman, their use of a carefully designed bow-and-arrow to affix the wire to the towers, and a mishap with the wire that nearly resulted in a last-second mission abort, Marsh's story is a succession of tense predicaments enlivened by the commentary of Petit, whose gregarious enthusiasm proves infectious.

The specter of doom hovers over this fantastic doc's every frame, the line separating life and death literalized in the form of Petit's wire hanging 1,300-plus feet above both Manhattan's concrete streets and those citizens staring upward in bewildered wonder. Throughout, Marsh never explicitly evokes 9/11 because he doesn't have to; every sweeping panorama of the mist-enshrouded towers - not to mention the very premise of a disguised foreigner surreptitiously sneaking into them to execute a monumental exploit - is more than enough to recall their ultimate, tragic fate.

Instead, the director lyrically synchronizes the build-up to Petit's historic performance with engrossing footage of the WTC's arduous, astounding creation by fearless laborers, the two linked visually via split-screen and thematically as incredible ambitions brought to life. And thus, as Man on Wire wends its way through the legal fallout and budding celebrity caused by Petit's stunt, what ultimately reverberates is this potent central association between Petit's endeavor and the Twin Towers' erection, two corresponding, peerless examples of human daring, creativity and ingenuity.