This taut series launch from bestseller Van Lente (The Con Artist) centers on the so-called Baltimore plot, whose participants sought to murder Abraham Lincoln before he could be inaugurated as president in 1861. Kate Warn (a fictionalized version of the real-life Kate Warne), the first female operative for Allan Pinkerton's National Police Agency, whose motto is "We Never Sleep," and a trainee, Hattie MacLaughlin, get handed a highly important assignment. The Philadelphia, Wilmington and Baltimore Railroad has hired the Pinkerton firm to protect Lincoln after reports surface that an attempt will be made on his life when he changes trains in Baltimore on his way to Washington. The plotters believe that murdering Lincoln will both throw the Union into turmoil and shift Maryland into the ranks of states joining the Confederacy. The perilous mission gives Hattie, who idolizes Kate, an opportunity to prove her worth. Van Lente is especially good at building the relationship between veteran Kate and newcomer Hattie, who only applied to the agency to be a secretary. Well-developed characters match the fast-paced plot. Readers will eagerly await the sequel. Agent: Jason Yarn, Jason Yarn Agency. (Mar.)