Katie Ledecky was powering through the final stretch of her 400-meter freestyle race, the point where she'd usually left the field far back in her wake. She was feeling good — "smooth and strong," in her words — when she looked to her left and realized she wasn't alone anymore.
"Oh," Ledecky thought, "she's right there."
"She" was Ariarne Titmus of Australia, a challenger four years younger than Ledecky, a challenger who caught and passed Ledecky for the gold medal. This, despite the fact that Ledecky posted her second-fastest time in the event ever, a time fast enough to have won every single 400-meter freestyle event in history .