In the third Girl Genius novel, Agatha Heterodyne returns to her ancestral home, the warped little town of Mechanicsburg. There she must claim her inheritance by convincing the artificial intelligence that animates her family's castle that she is, in fact, the new Heterodyne. But this apparently simple task is made complicated in several ways: An imposter claiming to be the legitimate heir appears. The Empire is convinced that Agatha is the person responsible for the Long War (and to be fair, they are not entirely incorrect). And, worst of all, the Castle itself is insane.