"Orphan Train" centers on 17-year-old Molly Ayer who is on the verge of aging out of the foster care system in present-day Maine. As required community service, she has to help 91-year-old Irish immigrant Vivian Daly, who as a child was shipped from New York City to Minnesota, to clean out her attic. Soon, the pair discover the parallels in their lives as outsiders, exposing a secret which has haunted Vivian her entire life.