John Jakes 
On Secret Service 

It is America 1861 and North and South have never seemed further apart: the threat of civil war hangs heavy in the air…For Lon Price, the issue is simple. He has inherited from his Methodist father both a burning sense of right and wrong, and a desire to see an end to slavery. So much so that he is prepared to resign from the Pinkerton police agency to fight for the North. But his departure is not necessary, for the federal government is well aware of the agency’s work, and in Lon they see a primie candidate for secret service… Margaret Miller is part of a family that prides itself on supporting the South: her father Calhoun is owner of the secession supporting Baltimore Independent; her brother Cicero has similar views, though the circles he moves in are considerably less law-abiding. When Calhoun is killed by a Yankee bullet, Margaret becomes as determined as Lon to uphold the ideals of her father…www.johnjakes.com