Posing as a Southern sympathizer named James Thomson in St. Catharines, Canada West, a hotbed of Rebel intrigue, Montgomery reunites with childhood friend Aaron Young, a once enslaved man who escaped the plantation of Montgomery's father and becomes an ally in the secret Union mission. To complicate his life further, Montgomery meets a Southern woman living in St. Catharines and falls in love.
Along the way, he also encounters famed Montreal photographer William Notman, as well as various spies and secret agents on both sides of the war in Toronto, Niagara Falls, Montreal, and Halifax, eventually crossing paths with Lincoln's future assassin.