By the smallest of margins, Torri Huske beat her U.S. teammate and managed to heal an old heartbreak at the same time.

100-meter butterfly

Credit...Daniel Berehulak/The New York Times

In third place at the turn on Sunday, Huske powered to gold, edging her teammate — and world-record holder — Gretchen Walsh at the end by touching just ahead of her. In a sport defined by infinitesimal slivers of time, that brief gap is either a flash or an eternity, and often it is both.

Huske missed out on an Olympic medal in Tokyo by one-hundredths of a second. On Sunday, she won gold by four-hundredths. And when she realized it, she said, “Oh my God,” and went to hug Walsh in the next lane.

Zhang Yufei, one of 23 top Chinese swimmers who tested positive for a performance-enhancing drug months before the Tokyo Games, won bronze. She won silver in Tokyo, nine-hundredths of a second ahead of Huske, who bested her — and everyone else — on Sunday night.