On the run! Union Engineer Braxton Wright thought his mission into the south was to extract the contents of a top secret Confederate train. Unbeknownst to him, he was a just a pawn in Alan Pinkerton’s plan to break his ace spy Hattie Lawton out of the Castle Thunder Prison. Now free, and in the company of Braxton’s childhood friend Laurie as well as a mysterious metal man, Braxton is itching to return north to his safe, quiet drafting board. But Hattie has other plans. Pinkerton didn’t arrange for her escape for no reason. She has something that the Union has been searching for since the start of the war — the location of the Alchemist who invented the Gray soldiers.

With the might of the Confederate army on their tale, Hattie and Braxton must make their way deep into the heart of the south and find the man who’s twisted genius brings dead soldiers back to serve. If Braxton can discover his formula, they just might be able to counter the Confederacy's’ greatest advantage.

Nipping at their heels, Colonel Beauregard Fuller of the Confederate Engineering Bureau also has a plan. If his agent can capture Braxton, the Union engineer might just be persuaded to serve him. With Braxton’s knowledge, the South could develop their own walking guns. With guns, Grays, and their dragons, the Union would have no hope of victory and be forced at last to let the Confederacy go!