What does a pocket full of buttons have to do with murder?

Henry's gift to Carrie for their eighth (month) anniversary is a journey on the Arkansas and Missouri Railroad's historic excursion train.  Destination?  Van Buren, Arkansas, a river town with a colorful past dating back to the early 19th Century.  But some of the people they see on the train arouse suspicion, and one of them ends up as a corpse on the bank of the Arkansas River--with a pocket full of tiny ivory-color buttons!  So begins another journey for the detecting pair, one that exposes traumatic events from Henry's past, and eventually takes the two of them to Kansas City and Henry's former life there as a police officer.  Will they catch a killer before more people die--including Carrie and Henry?  What makes people strong?  Is Carrie strong enough to take a bullet for one she loves?