Spoiler Alert! By its very nature, this page will give away the plot.

BASIC BACKSTORY
Girl Genius has been being written for some time now, and there have been a lot of twists and turns in the story. Not all of that is covered here, because really, beyond a certain point it's just easier to read the story itself, but this should be enough to get you up to speed:

The setting: In a time when the Industrial Revolution escalated into a full-on war, rival mad scientists, (“Sparks” to be polite), are the ruling powers in most of Europe. Keeping them all in line is Baron Wulfenbach, a particularly powerful and cranky Spark who, when someone starts causing trouble, simply steps in and makes them stop. His captial is the gigantic airship fortress Castle Wulfenbach.

The main character: Agatha Clay was a student at Transylvania Polygnositc University, who had truly rotten luck until she was revealed as a Spark. (Some might argue that this, also, was rotten luck.) She has also recently discovered that she is the last of the famous Heterodyne family—beloved heroes who disappeared under mysterious circumstances many years ago. Folk legend claims that they will someday return, but so far they haven’t managed it.