The Shut Mouth Society (The Best Thrillers Book 1);

When a rich Santa Barbara collector acquires a newly discovered Abraham Lincoln document, he asks detective Greg Evarts and UCLA professor Patricia Baldwin to authenticate it. Their research launches them into a dangerous struggle with a secret society formed during Reconstruction. Before they can solve the mystery surrounding the Lincoln manuscript, a shocking murder forces them to run for their lives.
 
As they race across the country, they discover a Civil War secret that could upset the balance of power in North America. Now Evarts and Baldwin must unravel the 150-year-old conspiracy before it’s too late … and before they are silenced for good.