Return to the world of the bestselling Greenglass House, where smugglers, magic, and pyrotechnics mix, in a new adventure from a New York Times bestselling, National Book Award nominated, and Edgar Award-winning author. Lucy Bluecrowne is beginning a new life ashore with her stepmother and half brother, though she’s certain the only place she’ll ever belong is with her father on a ship of war as part of the crew. She doesn’t care that living in a house is safer and the proper place for a twelve-year-old girl; it’s boring. But then two nefarious strangers identify her little brother as the pyrotechnical prodigy they need to enact an evil plan, and it will take all Lucy’s fighting instincts to keep her family together. Set in the magical Greenglass House world, this action-packed tale of the house's first inhabitants reveals the origins of some of its many secrets.

Lucy Bluecrowne and Maxwell Ault are on a mission: find the three pieces of a strange and arcane engine. They're not exactly sure what this machine does, but they have it on good authority that it will stop the war that's raging between their home country of England and Napoleon Bonaparte's France. Despite being followed by mysterious men dressed all in black, they're well on their way to finding everything they need when their ship, the famous Left-Handed Fate, is taken by the Americans. And not just any Americans. The Fate (and with it, Lucy and Max) are put under the command of Oliver Dexter, who's only just turned twelve. But Lucy and Max aren't the only ones trying to put the engine together, and if the pieces fall into the wrong hands, it could prove disastrous. Oliver is faced with a choice: help Lucy and Max and become a traitor to his country? Or follow orders and risk endangering that same country and many others at the same time—not to mention his friends?