They hail from the same metro area and swim in the same event. But things could not have turned out more differently for Katie Ledecky and Kate Ziegler on Thursday in London.

Ledecky, the 15-year-old prodigy and youngest of the Team USA swimmers at the Olympics, won her heat in the 800-meter freestyle race in a time of 8:23.84 and advanced to Friday's final. Only Great Britain's Rebecca Adlington (8:21.78) and Denmark's Lotte Friis (8:21.89) did better in the four other heats. Ledecky, a sophomore at Stone Ridge High in Bethesda, will try to upset those veterans and make it to the podium with a medal around her neck.

Drive up Wisconsin Avenue out of Bethesda, and the marquee at the base of Stone Ridge's campus shouts its support for Ledecky to the drivers speeding north on the busy road. It is the kind of idealistic enthusiasm that once greeted Ziegler during her days at Bishop O'Connell in Arlington. She, too, was a young, successful prodigy and for a long time delivered upon that promise. But a disastrous trip to Beijing for the 2008 Olympics soured Ziegler on the sport, and she all but retired in the aftermath.

Tentatively, she returned and by this summer was again a candidate to medal at the Olympics. Unfortunately, her meet ended in frustration again. This time it was the flu that did her in, sapping Ziegler's energy in recent days as she finished last in her heat (8:37.38). She missed the cut for the final by more than 10 seconds and placed 21st overall. Afterward, Ziegler broke down in tears during her postrace press conference, her Olympic dreams shattered for the second time.

"I came into this race thinking I was going to fight and do the best I could," Ziegler said, according to the Los Angeles Times. "And that's what I did."

It is the great chasm of emotion in these events and why millions of viewers are compelled to watch sports they otherwise rarely pay attention to. Ledecky may one day know Ziegler's pain. But for now her dreams are still very much alive.

- Brian McNally