Girl Genius: Agatha H and the Clockwork Princess -- Paperback / softback

After escaping from the massive airship known as Castle Wulfenbach, Agatha falls in with a travelling troupe of performers, where she begins training under Zeetha, swordmistress and princess of the lost city of Skifander. With Wulfenbach on her trail, it's going to take more than a spark of Mad Science for Agatha to traverse the treacherous wasteland of war-torn Europa.