This story was published in partnership with The 19th , a nonprofit newsroom reporting on gender, politics and policy.

Editor's note: This reporting involves sexual violence against children and may not be suitable for all audiences. You can click the red LISTEN button above to hear the audio version of this story, produced by Jackie Harris, with music from Blue Nocturnal, Cauldron, Lillehammer, The Cabinetmaker, Trailhead and Blue Dot Sessions.

Erin Moulton’s interest in genealogy was casual at first. It started when people began stopping by her desk at the Derry Public Library with questions about the 198-year-old New Hampshire town’s history or for help looking up their ancestors.

Moulton, 43, soon developed an obsession with solving these history puzzles, chasing a “geeky” kind of

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