An installment in the continuing story. With spoilers ahead for the earlier ones. This one continues the process begun in the last, of really raising the stakes.
In the opening, we have a day in the life of Mechanicsburg, and the Circus accepts Wooster's offer of a refuge in England. Agatha detaches herself. Not only did her mother -- er, Lilith/Judy, the foster mother -- tell her to go to Mechanicsburg, she knows that she needs it to do anything. Meanwhile, the Baron is in the hospital there.
When you read her arrival, be sure to check out the signs advertising things. A good knowledge of webcomics will help -- interpret them.
Once there -- we have a mad medley of plot. Involving more assassins than you can shake a stick at, Gil's new invention, another girl Agatha's age who claims to be the Heterodyne heir and whose airship is pink, a coffee shop and discovering why Lilith did not approve of stimulants (such as coffee) for young ladies, a visit to the crypt, an explanation of why most people expect a boy heir, an attack on the city, tales of the mad castle in the center of town, which has been under repair for over a decade, and a foolish attempt to arrest Agatha. All concluding with Agatha's doing the only logical thing, even if it raises the stakes again.