Set in Ireland, 1895 in a steampunk fantasy world. When Molly Madigan's grandfather is killed by his partner, Gustav and his inventions stolen, Molly begins a quest to take back what is rightfully hers. Twenty years later, in Wichita, Kansas, an unwitting postal clerk discovers a mysterious box containing the Potestatum, Molly's grandfather's most powerful invention. But, after many long years of hunting for the Potestatum, Gustav is hot on the trail. He tracks down Molly, and a battle for the ultimate weapon ensues.