Lionel Barrymore played Milt Shanks, the "Copperhead" of the title, on stage and repeated the role for this Paramount studios release. The patriotic story of Civil War days (originally a novel by Frederick Landis) involves Shanks' tenure as President Lincoln's most dedicated secret service man. For 40, years as a spy, he pretends to have sympathy for the Confederacy, in spite of the shame it brings his family and the scorn shown by those around him. Barrymore's wife, Doris Rankin, appeared in both the play and the film, but as Ma Shanks, not Milt's wife, Madeline. That role went to a younger actress, Anne Cornwall.
by Janiss Garza synopsis