Hoping to shift the balance of power in the United States' Civil War, the League of Darkness heads across the Atlantic in the Prometheus while being pursued by the crew of the Aurora. When the Aurora crashes, Phileas, Rebecca, Jules, and Passepartout are welcomed into the home of a true Southern belle, Saratoga Browne, with whom Phileas falls in love. Passepartout and Rebecca join forces with the Union to try and defeat the Prometheus, while Phileas and Jules go after the airship when Count Gregory kidnaps Saratoga to force Phileas' hand. Jules manages to distract the airship's crew while Phileas rescues Saratoga. Count Gregory uses the power of the ship to reassemble his component parts into an indestructible cyborg, but a gunshot from the Union cannons knocks him out. Phileas and Saratoga escape by parachute, but a final gunshot from Gregory kills Saratoga just as Phileas proposes marriage to her. The Prometheus is brought down, leaving a despondent Phileas.