Eleven-year-old orphan Nell Warne arrives on her uncle's doorstep in 1859 Chicago with a secret—she's the niece of America's first female detective, Kate Warne. When her uncle initially rejects her, Nell uses her sharp wits to prove her value by helping Kate solve a dangerous case involving counterfeiters and a plot to assassinate President-elect Abraham Lincoln. This historical adventure follows Nell as she navigates the male-dominated world of the Pinkerton National Detective Agency, discovers family secrets, and learns that courage comes in many forms.