In the annals of ballet, Tanaquil Le Clercq is a mythical presence. She was "an elongated, stretched-out path to heaven," says fellow dancer Jacques d'Amboise. "Her limbs," the great Maria Tallchief explains, "never finished." But Nancy Buirski's documentary is really the first fount of actual information on the full life of the dancer who moved like a birch tree come to life. And this time, knowing more makes the story even better.

Tanny died in 2000 at age 71, but plenty of people considered her dead at 27. That's when, at the height of her powers, she contracted polio. She'd been standing in a vaccination line with her fellow dancers before their European tour, but she ducked out at the last second to preserve strength, saying she'd do it after the tour. She fell ill in Copenhagen and never danced again.

"Truly," Buirski told a New York audience in a talk, "I was seduced by Tanny." Even through the haze of degraded black-and-white film, her dancing is rapturous. Buirski collected every bit of footage she could find and added intimate letters, photographs, and interviews with friends rather than experts.

Tanny was married to George Balan­chine, the 20th-century titan choreographer who made a practice of marrying his muses, one after another. Balanchine comes across as creepy, no doubt. But the exploitation went both ways, and Tanny was no victim. From her wheelchair, she taught, entertained, wrote books. In letters, she points out that all dancers have naturally clipped careers but not all have rich entire lives. The big surprise is that she could be almost as rapturous in her chair as on her feet. recommended