The murky sexual politics aside, the Wilis provide ballet with a highly prized treasure: a gorgeous outing for the corps de ballet. Visually the Wilis are heaven sent, dancers cloaked in flowing white, ethereal and appearing to float. They’re willowy spirits with an edge — dreamy but fatal. They thus embody the paradox underlying all ballet, a craft of technically unnatural moves that the dancer’s art renders exquisite. Everything may be beautiful at the ballet, as “A Chorus Line” tells us.

But beware. And go alone at your own risk.