Sean McCann was just two years old when his older sister Madeleine vanished on a family holiday in Portugal. Nearly two decades later, the 21-year-old will stand on the starting blocks at the Tollcross Swimming Centre in Glasgow — not as a spectator, but as a competitor representing Scotland at the Commonwealth Games.

McCann, a Loughborough University student, made his debut at a major championship Saturday in the 400-meter freestyle heats. He's also entered in the 800-meter and 1500-meter freestyle events, a demanding triple that showcases his endurance as a distance swimmer.

"I'm very excited," McCann told Loughborough University. "It's my first senior Games so I'm just looking forward to representing Scotland and doing my absolute best." He called competing at a home Commonwealth Games "the pinnacle" of his career so far, especially since he has family in Glasgow who will be watching.

The timing holds particular meaning for McCann. He attended the 2014 Commonwealth Games in Glasgow as a nine-year-old, watching the action from the stands. Twelve years later, he'll be the one in the pool. "To make it now, 12 years later, is really a full-circle moment," he said.

McCann grew up in England but qualifies to swim for Scotland through his father, Gerry McCann. He and his twin sister were toddlers in 2007 when Madeleine, then three years old, disappeared during a family vacation in Praia da Luz, Portugal. The case became one of the most closely watched missing-person investigations in the world and remains an ongoing Metropolitan Police matter.

While the shadow of that unsolved case has followed the family for nearly two decades, McCann's achievement marks a moment of individual triumph. He joins a long tradition of athletes using sport as both an escape and a destination — a young man from England building his own identity through the water, now representing a nation that embraced his family's story years ago.

The heats begin Saturday morning, with McCann's family in the stands to cheer him on. For a swimmer who once watched the Commonwealth Games as a child, this is the moment he gets to do the swimming.