"In a steam-powered world, Miss Constance Haltwhistle is the last in a line of blue-blooded rogues. Selling firearms under her alias, the "Brass Queen," she has kept her baronial estate's coffers full. But when US spy J. F. Trusdale saves her from assassins, she's pulled into a search for a scientist with an invisibility serum. As royal foes create an invisible army to start a global war, Constance and Trusdale must learn to trust each other. If they don't, the world as they know it will disappear before their eyes." --Back cover.