In the midst of Sarah and Frank's wedding preparations, Sarah accompanies her mother on a condolence call to the Upper West Side, where Charles Oakes, the son of family friends, has died unexpectedly after suffering from a mysterious disease. But Charles's father believes his son was poisoned, and would like Sarah and Frank to look into the matter with the utmost discretion.

Putting off their own personal affairs, Sarah and Frank soon learn that not everyone wants to know more about Charles's death, particularly if he was murdered. As they unravel secrets that reach back to the Civil War, they also discover that they are in the company of a very present danger...