13-year-old Ermin is a gifted mechanic and the worst student at St. Anselm's Training School for Orphans. She's just failed her exams for the third time-something nobody's ever done. Worse, Ermin's been running her own repair business for money, something that's expressly forbidden. If the headmistress finds out, Ermin will go to prison. Her future will be over before it's even begun.

But that's not her only secret.

Her best friends, Colin and Georgie, are wizards in a world where magic is strictly controlled. Ermin worries that her friends will be captured, drained of their power, then banished. When Georgie's caught aiding the Wizard's Resistance, Ermin repairs a broken flying carpet so all three of them can escape.

Hesitant to join the Resistance because of her lack of magical power, Ermin steals an experimental device from a wizard hunter that could destroy every wizard in the Creek. She's faced with a choice: either smash the device or convert it into a different kind of weapon-one that not only helps wizards but just might get her an apprenticeship at the prestigious Guild Academy.

Ermin's got one chance to get it right. If she fails, she risks losing her two best friends... and her dreams.