Tommy Powell, age 7, had just finished his Rocky Road ice-cream cone when he sneezed.

"Daddy," he said, looking into the depths of a large grate on Conneticut Avenue, "I lost my braces."

His father, Austin T. Powell, a Capitol police officer, didn't know quite what to do, so he took Tommy home to Dale City and broke the news to his wife that "$1,800 worth of braces" had gone aglimmering.

"Tommy was scared to death because he thought we were going to punish him," Yajaira Powell said, "to take it out of his allowance." A trip back to Conneticut Avenue confirmed that the braces were there, 40 feet down glinting in the Tuesday evening light. But whose shaft was it?

By Thursday, after a barrage of phone calls, the search had narrowed to Metro, and director of public affairs Cody Pfanstiehl was able to confirm that it was a subway ventilation shaft.

At 1:10 a.m. yesterday, after trains had stopped running, the intrepid Pfanstiehl and track maintenance supervisor Dave Short descended into the Farragut North Station, journeyed a block and a half underground, climbed a 10-foot ladder, navigated past the giant ventilation fans and finally reached the botton of the shaft where Short began an inch-by-inch search among the puddles, bottles tops and cigarette butts.

At 1:45 a.m., Short and Pfanstiel emerged, clutching the braces in triupmh.

Tommy, who left on a vacation yesterday, will be reunited with his braces when he returns from Venezuela on July 26.