In New York, a city defined by its hurry and bluster, unexpected moments of kindness or grace become a kind of communion, a unifying ritual. Street musicians who are actually talented, a flock of 4-year-old day campers, a public romantic gesture-- all make us pause in unison and reflect, at least for a few seconds.

Perhaps the greatest of all these moments happened when the city was at its weakest. In 1974 the monumental World Trade Center had just been built, but the city was sliding into recession, in a decade marked by blackouts and crime waves. One August morning a bold Frenchman walked out between twin towers and, seemingly walking on air, danced for the astonished crowds below.

The story of how he got there, and why the hell he was out there to begin with, is told in Man on Wire, an energetic yet contemplative documentary. Philiippe Petit, 24 at the time of the World Trade Center walk, had already surreptitiously strung a wire between the spires of Notre Dame as well as the towers of a Sydney bridge, dazzling passersby and infuriating cops, who promptly arrested him. But Petit claims he had dreamt of walking between the twin towers ever since he learned of their existence as a child. Determined, and perhaps a little deranged, Petit set out to fulfill his childhood fantasy.

No one would give him permission to execute the walk, of course, so Petit would have to sneak in at night, carrying the myriad equipment necessary to string a cable between two buildings 200 feet apart. He teamed up with a motley crew of cohorts, from childhood friend Jean Francois and Petit's girlfriend Annie to several New Yorkers, including an attorney who worked in the building.

Most of the accomplices, including Petit, are interviewed for the film, their stories supplemented by a handful of snazzy re-enactments and some surprisingly intimate original footage. Each interviewee looks back with equal parts wonder and exasperation at Petit, who could alienate his friends with his single-minded obsession with the walk. Jean-Francois fights with him especially, and his frustration tells as much about Petit's personality as the extensive interviews with him. But Petit remains endearing throughout, the kind of enigmatic made-for-Hollywood figure who embraces fame as his birthright. It takes one kind of man to walk on a tightrope thousands of feet in the air, but it takes another to taunt the policemen who eventually arrive to arrest him.

Playing like a heist film in the re-enactments of the WTC break-in, not to mention the exhilarating footage of Petit's walk, Man on Wire is thrilling in a way few documentaries about such a light subject ever get to be. It's a trifle, probably, but an utterly engaging one, and a reminder of the kind of rare moments that make everyone turn to the sky and just say “Wow.”