In the midst of the American Civil War, President Abraham Lincoln, aware that the conflict is winding to an end, becomes intensely committed to ensuring the passage of the Thirteenth Amendment to the Constitution, which will formally abolish slavery in the United States. Despite the raging war, Lincoln recognizes a narrow window of opportunity to bring the amendment to a vote while the nation is still divided. He contends with the complex political machinations required to secure sufficient support from a fractious Congress. While Democrats vehemently oppose the amendment, Lincoln must also contend with conservative factions within his own Republican Party, facing the challenge of rallying the disparate interests toward a common cause.

As Lincoln drives the amendment forward, he employs a mixture of persuasion, patronage, and political pressure to secure the necessary votes, even as he grapples with the moral and legal implications of his actions. He navigates the political landscape with the aid of Secretary of State William Seward, who orchestrates behind-the-scenes deal-making with both lame-duck Democrats and reluctant Republicans. In his personal life, Lincoln deals with the emotional distress of his wife, Mary Todd Lincoln, who is deeply affected by the death of their son Willie and the ongoing war. His relationship with Mary and his other children adds another layer of complexity to his character, as does his interaction with soldiers and ordinary citizens, revealing a president deeply humane and determined amidst one of the most tumultuous times in American history.