Based on a true story from the author's family history, Jarrettsville begins in 1869, just after Martha Jane Cairnes has shot and killed her fiancé, Nicholas McComas, in front of his Union cavalry militia as they were celebrating the anniversary of the Confederate surrender at Appomattox.

To find out why she murdered him, the story steps back to 1865, six days after the surrender, when President Lincoln has just been killed by John Wilkes Booth. Booth belongs to the same Rebel militia as Martha's hot-headed brother Richard, who has gone missing along with Booth. Martha is loyal to her brother but in love with Nicholas McComas, a local hero of the Union cause, and their affair is fraught with echoes of the bloody conflict just ended.

The story is set in Northern Maryland, six miles below the Mason-Dixon line, where brothers literally fought on opposing sides, and former slave-owners live next door to abolitionists and freed men. Such tension proves key to Martha's motives in killing the man she loves, and why - astonishingly - she is soon acquitted by a jury of her peers, despite more than fifty eyewitnesses to the crime.