It is 1828. Fate has brought four people together in a modest house in Abingdon, Virginia. All of them have experienced great losses in their lives, with the three adults consumed by their grief and regret. The fourth, an innocent, is a recently orphaned young boy working through his own sadness but learning to adapt to his new living situation.

Alexander Dromgoole, a Revolutionary War veteran and Indian trader, is a frail and ailing old man, living out the last years of his life being boarded out by the town's Overseers of the Poor. He wonders how his life had taken this turn, considering in years past, he participated in some of the most important events in the history of America. He once had so much, and yet he has lost everything.

Letters Unposted tells Alexander's adventure-filled story through letters he wrote to his brother over a period of fifty years. Due to failing eyesight, he has the young boy, Thomas, read them back to him, reviewing his life one last time before he dies.

How will Alexander's letters affect the members of the household, reopening old wounds and causing them to reexamine painful events of the past? Will they be able to find acceptance and the self-forgiveness needed to create new bonds and start life anew?