In March 1900, as former Congressman John Bingham of Ohio lies dying, he begins to tell a strange tale to his physician, Dr. Jamie Fraser. Bingham famously prosecuted eight members of John Wilkes Booth's plot to kill Lincoln. But during the 1865 trial, conspirator Mary Surratt divulged a secret so explosive it could shatter the republic. Though Bingham takes the secret to his grave, Fraser cannot let go of the mystery. Bored with small-town medical practice, he begins to investigate, securing an unlikely ally in Speed Cook, a black, college-educated professional ballplayer and would-be newspaper publisher. Cook is fascinated by Fraser's inquiry and, like Fraser, thinks the accepted version of Lincoln's assassination rings false. Was Booth truly the mastermind or were other, more powerful forces pulling the strings?