An Enigma Solved

A story within a story, this is a romantic novel in the style of the 1940's, which means it is brief, simple, plausible and clean. The first protagonist, a Hessian Lt. with Burgoyne's Army at Saratoga in 1777, and an ancestor of the author, is sent with dispatches to General Cornwallis at Charleston. On a subsequent (fictional) trip his troop is ambushed carrying a British war chest of gold intended to equip Scottish Royalist troops in the Georgia hills. Although wounded he is not captured through the kindness of the then Mistress of the Fair Oaks Plantation who secrets him in a hidey-hole of the mansion.
What subsequently happens to him is unknown until 1909 when his diary is found between the thick walls of the mansion intact and legible. Legible except that the last pages are written in some strange code and cannot be read.
In 1946 Ab Andrus, the only Inheritance Investigator in the South is requested by the State of Georgia to make a formal statement as to the authenticity of the Diary.
Like the Hessian he gets to know too warmly the current Mistress of Fair Oaks and both couples learn a great about themselves and each other in their contacts made in the search. One wins his lady and the other does not.