One aspect of the aftermath of the assassination of US President Abraham Lincoln is dramatized. Immediately after the fact, the authorities learn that despite the Civil War having officially ended, the assassination was only part of a larger "southern" conspiracy also to assassinate Vice-President Andrew Johnson and Secretary of State William H. Seward. Most of the proverbial "shooters" are also known in not hiding their identities in the attempts. While Lincoln's assassin, actor John Wilkes Booth, a Confederate sympathizer, is assassinated himself shortly thereafter, several others are arrested including one female, Mary Surratt, in whose boarding house the other conspirators often met. In the military trial of which Surratt is a part, Maryland Senator Reverdy Johnson is assigned her attorney. Feeling unable to try the case himself, Johnson in turn assigns the case to his underling, a reluctant Frederick Aiken, who, as a previous Union soldier, does not want to defend someone who conspired to kill for the rights that he fought for. Surratt is indeed a proud southerner but an even more protective mother. Given a possible out by Johnson from trying the case which does take a toll on his personal life for defending someone like Surratt, Aiken begins to have doubts as to her guilt and begins to believe that she is being used as a surrogate for her son, John Surratt, the true criminal who has gone into hiding, especially problematic as the proceedings are stacked against Surratt and thus by association him as Secretary of War Edwin M. Stanton wants to find her guilty, true guilt or not, in the absence of her son solely for the sake of national peace.