In the 1860s, the Copperheads were a vocal faction of Democrats in the Northern United States of the Union who opposed the American Civil War, wanting an immediate peace settlement with the Confederates.
In a rural community upstate New York in 1862, farmer Abner Beech is a Northern antiwar Democrat. While his neighbors take up the Union cause in the ongoing American Civil War, Beech believes that coercion in resisting the secession of the southern states is unconstitutional, and gradually becomes more and more harassed for his views, derisively called a "Copperhead". His son, Thomas Jefferson Beech, enlists in the Union Army. Beech also arouses the ire of militant abolitionist Jee Hagadorn, whose daughter Esther (Lucy Boynton) loves Jeff.