Following the death of Saratoga Browne, Jules, Rebecca, and Passepartout have their hands full with a suicidal Phileas. Packing up the Aurora, they decide to go on a tour of the United States. They meet up with a young boy, Al, who they find is mechanically inclined and partially deaf. He is also an incredible mechanical genius, having recreated the design of the Cardinal's Chariot (from "The Cardinal's Design). It lacks time-travel capability, but the miniature armored model can hover and move. Phileas' current gambling partner, an arms dealer, finds out about Al and his invention, and decides to finance it with the help of the Union. The others browbeat Phileas into financing a hearing operation for Al - they go to find the boy and find out about the creation of the new tank. Concerned that it will disrupt the balance of power between the Union and the Confederacy, the group resolves to stop it.