Of all the astonishing works in Cai Guo-Qiang's exhibition "I Want to Believe" at New York's Guggenheim Museum, the one I can't get out of my head is "Head On." The piece consisted of 99 full-size synthetic wolves stampeding up the museum's spiral ramp with such force that the front of the pack lifts up into an arc of flight, like Santa's reindeer—only to crash headlong into a wall of glass. Oof! Cai is best known for art events using choreographed explosions—shown off to spectacular effect at the opening ceremonies of the Beijing Olympics—and his art is filled with multiple meanings: celebratory but also resonant of war and terror. Those wolves are as cuddly as any furry toy, but also as scary as snarling animals. Maybe they linger in my memory because so much has happened since they careered through the museum last spring. Now there's the wolf at every door. That wild pack of Wall Streeters that finally hit the wall. Or perhaps it's just the quieter hint in "Head On" that every living creature is racing toward oblivion.