Between 1854 and 1929, so-called orphan trains ran regularly from cities on the East Coast to the farmlands of the Midwest, carrying thousands of abandoned children whose fates would be determined by pure luck. Inspired by these little-known events in American history, Orphan Train weaves together the stories of Vivian Daly, a 91-year-old Irish immigrant who as a child was shipped from New York City to Minnesota on one of thousands of 'orphan trains' and Molly Ayer, a 17-year-old who is on the verge of aging out of the foster care system in present-day Maine. An unlikely friendship develops between the two women when Molly is "hired" to help Vivian clean out her attic as required community service, and soon discovers the parallels in their lives as outsiders, exposing a secret which has haunted Vivian her entire life.