On a summer weekend in 1982, Barre, Vermont was crowded with music, traffic, and thousands of people moving through town for an annual festival. Somewhere in that noise, an 18-year-old woman disappeared.

In the days that followed, investigators tried to make sense of what little they had: fragments of sightings, possible suspects, conflicting leads, and tests that seemed to narrow the field. But the case did not move cleanly from suspicion to arrest.

Decades later, the same investigation that was first shaped by uncertainty was reopened by science. And this time, the evidence pointed back to someone investigators had once left behind.