It's 1905. Scottish spy Ranald MacKenzie, suffering from "Soldier's Heart," is plucked from his desk job when a report filters in that the Kaiser of Germany and Tsar of Russia are secretly communicating about an alliance to unite the major powers of Europe against Britain. MacKenzie is sent on a sensitive mission to defuse the situation and prevent a world war. Battling anxiety and uncertainty, he soldiers on, fortified by his love of country and his faith in God.

MacKenzie is partnered with a beautiful, mysterious agent claiming to be Catriona Cameron, who is reported "missing" in Germany. She is a woman haunted by her own secret memories of a terrible event that forever changed her life. Smart, unpredictable, and-in MacKenzie's eyes- immoral, Cameron will do whatever it takes to complete the mission.

Trailing the pair's steps lurks Leopold Tirpitz, German Intelligence's foremost interrogator. He is desperate to catch the spies lest his own secrets be revealed.

As events intensify, MacKenzie and Cameron race against time to save lives. And the question remains: How far can you go before your compromise your honor?