In January 1865, United States President Abraham Lincoln expects the Civil War to end soon, with the defeat of the Confederate States. He is concerned that his 1863 Emancipation Proclamation may be discarded by the courts after the war and that the proposed Thirteenth Amendment will be defeated by the returning slave states. He feels it imperative to pass the amendment beforehand, to remove any possibility that freed slaves might be re-enslaved.

The Radical Republicans fear the amendment will be defeated by some who wish to delay its passage; support from Republicans in the border states is not yet assured. The amendment also requires the support of several Democratic congressmen to pass. With dozens of Democrats being lame ducks after losing their re-election campaigns in the fall of 1864, some of Lincoln's advisors believe he should wait for a new Republican-heavy Congress. Lincoln remains adamant about having the amendment in place before the war is concluded and the southern states are re-admitted.

Lincoln's hopes rely upon Francis Preston Blair, a founder of the Republican Party whose influence could win over members of the border state conservative faction. With Union victory in the Civil War highly likely but not yet secured, and with two sons serving in the Union Army, Blair is keen to end hostilities quickly before the spring thaw arrives and the armies march again. Therefore, in return for his support, Blair insists that Lincoln allow him to engage the Confederate government in peace negotiations. However, Lincoln knows that significant support for the amendment comes from Radical Republicans, for whom negotiated peace is unacceptable. Unable to proceed without Blair's support, Lincoln reluctantly authorizes Blair's mission.

In the meantime, Lincoln and Secretary of State William Seward work to secure Democratic votes for the amendment. Lincoln suggests they concentrate on the lame-duck Democrats, as they will feel freer to vote as they choose and soon need employment; Lincoln will have many federal jobs to fill as he begins his second term. Though Lincoln and Seward are unwilling to offer monetary bribes to the Democrats, they authorize agents to contact Democratic congressmen with offers of federal jobs in exchange for their support. Meanwhile, Lincoln's son, Robert, returns from law school and announces his intention to discontinue his studies and enlist in the Union Army, hoping to earn a measure of honor and respect outside of his father's shadow before the war's end. Lincoln reluctantly secures an officer's commission for Robert. The First Lady is aghast, fearing that he will be killed. She furiously presses her husband to pass the amendment and end the war, promising woe upon him if he should fail.