As the nation relishes the moment on April 14, 1865, celebrating the end of the Civil War marked by General Robert E. Lee's surrender at Appomattox Court House in Virginia, Frederick Aiken (lawyer and Union veteran), alongside his closest allies William Thomas Hamilton and Nicholas Baker, as well as his wife Sarah Weston, immerses himself in the jubilant atmosphere. Yet, the night of festivities quickly turns into a nightmare as a pivotal series of events unfolds, destined to alter the trajectory of American history forever.
On this tragic night, John Wilkes Booth seizes the moment to instill terror among those who championed freedom and equality. He brazenly enters Ford's Theater and shoots President Abraham Lincoln in the back of the head while the President enjoys the play Our American Cousin. In the chaos, Booth also stabs Henry Rathbone, a guest at the Presidential box, and boldly leaps onto the stage, proclaiming, > “Sic Semper Tyrannis! The South is avenged!” before making his hasty escape to Maryland.
As the shocking news of Lincoln’s assassination spreads rapidly, Aiken, along with Hamilton and Baker, watches in horror as the critically injured President is taken to a nearby boarding house, where he succumbs to his wounds early the next morning. With this profound loss, Vice President Andrew Johnson ascends to the presidency, ushering in a new and turbulent era. In the wake of this calamity, Secretary of War Edwin Stanton mandates the arrest of all suspects, including Mary Surratt.
While Booth and David Herold manage to elude capture for several days, their luck runs out when Union soldiers uncover the barn where they suspect the conspirators are hiding and set it ablaze. Herold surrenders, but Booth meets his end at the hands of Sergeant Boston Corbett when he brandishes his rifle at the approaching soldiers.
As authorities intensify their search for John Surratt, Mary’s son, Mary Surratt’s defense falls into the hands of Mary Surratt’s Defense Attorney Reverdy Johnson, a Maryland Senator and Aiken's boss. However, impeded by his Southern sympathies, he struggles to mount an effective defense and eventually solicits Aiken’s help, a Northerner, to take on Mary’s case alongside co-defendants Michael O'Laughlen, Edman Spangler, Samuel Mudd, and Samuel Arnold.
Upon entering Mary’s cell, Aiken is met with her anxious gaze imploring him to check on her daughter, Anna, who lives in the boarding house rife with murmurs of conspiracy. With a solemn sense of duty, Aiken agrees, his footsteps echoing through the dim corridors as he embarks on a quest for clues that may either vindicate or implicate Mary. In a significant moment, Aiken discovers a ticket with the initials “LJW” (belonging to Louis J. Weichmann), a seminary friend of John who had clandestine ties to Booth, revealing layers of deceit soon to unfold in court.
As Weichmann testifies, his words sketch a vivid narrative of John's covert meetings with Booth and other key figures like Herold, Powell, and Atzerodt who frequented Mary’s boarding house. Aiken astutely dissects Weichmann's statements, casting doubt on his credibility and weaving a complex web of guilt.
Despite his growing misgivings about Mary's innocence, Aiken seeks to confront her again. She introduces an alternative perspective, asserting that John and his associates originally planned to kidnap Lincoln rather than kill him. She states that Booth intervened, misinforming them of the President's whereabouts just two weeks before. The silence from Anna during Aiken's inquiries reinforces the loyalty that Mary commands from her family.
In the courtroom, Chief Prosecutor Joseph Holt calls innkeeper John Lloyd to testify, painting Mary as the orchestrator behind the assassination plot. Lloyd claims she provided him with binoculars and instructed him to prepare pistols and whiskey for the night of Lincoln's assassination. Aiken's incisive questioning reveals Lloyd's admitted alcoholism, leading to a volatile scene as he is dragged out of the courtroom in a fit of rage.
Upon entering the prestigious Century Club, Aiken faces a harsh revelation: his membership is revoked due to his steadfast defense of Mary. This news triggers a confrontational argument with Sarah, culminating in her disowning Aiken and leaving his life. Striving for solace, Aiken pleads with Anna to testify for her mother, whose sworn statement shifts the blame for Lincoln's assassination onto her brother John.
Anna’s testimony instigates a visit from Father Jacob Walter, who has been tending to Mary during her imprisonment. Despite claiming ignorance regarding John's location, Aiken seizes the opportunity to relay a message to John through Walter, warning him of his mother's impending execution unless he surrenders.
As the judicial process unfolds, Mary Surratt is found guilty on all charges and is sentenced to life in prison. However, with Stanton's influence, her fate is altered, and she faces execution alongside Powell, Herold, and Atzerodt, while Mudd, Arnold, O'Laughlen, and Spangler are similarly condemned to prison.
Aiken remains unyielding in his pursuit, obtaining a writ of habeas corpus from Judge Andrew Wylie to challenge Mary’s sentence. However, President Johnson swiftly nullifies this writ, leading inexorably to the grim execution of four condemned prisoners.
Fifteen months later, Aiken visits John Surratt, who has been captured abroad and is now imprisoned. Despite John’s gratitude for Aiken’s kindness towards his mother, he dismisses the rosary Aiken extends as a gesture of comfort. This poignant exchange foreshadows the landmark ruling by the U.S. Supreme Court a year later, which establishes the fundamental right of citizens to be tried by a civilian jury—even during wartime (Ex parte Milligan).
As the tumultuous chapters of this saga draw to a close, Aiken turns away from the courtroom battles and embraces a new role as The Washington Post's first City Editor, marking the dawn of an exciting new journey in his life.
