The American Civil War continues unabated. The opposing sides are armed with monstrous mechanisms - combat airships, walking combat vehicles, powerful and maneuverable artillery. Death reaps a rich harvest on the battlefields, and in hospitals there is a battle with itself. Sister of Mercy Mercy Lynch faces pain and suffering every day. Before she has time to recover from the news of the death of her husband, who fought in the ranks of the northerners, she learns that her father is seriously ill. The young woman decides to find him in distant Seattle, which will require her to cross a war-torn country. A whim of fate brings her onto the famous Dreadnought armored train. However, the Dreadnought is shrouded not only in glory, but also in mystery...