Lord of Air and Darkness - S1.E7

While investiging a country priest's murder, Jules is lured to a secret base of the League of Darkness, where they are creating a flying ship called the Prometheus. Jules accepts a commission at the behest of the ship's beautiful commander, unaware of the League's true purpose. The others come to investigate, and the Aurora is taken captive. Rebecca discovers that the League plans to use both ships to help the Confederacy win the Civil War. While Phileas confronts the League's leader, the centuries-old "cybernetic" Count Gregory, Jules turns against the League. Phileas and Passepartout recover the Aurora, while Jules is forced to choose between the commander and Rebecca. He goes with Rebecca, and the two manage to escape. The episode ends with the Aurora giving chase to the Prometheus as it heads west to the United States.