In this third book in the exceptional Curiosity House mystery series by bestselling author Lauren Oliver and mysterious recluse H. C. Chester, four children must uncover the evil Nicholas Rattigan's newest dastardly scheme, wage war with a rival freak show, and deal with a spy who may have infiltrated their happy home.

Sam, Philippa, Thomas, and Max have just started to recover from their capture and subsequent escape from Rattigan. But the children's lives don't stay quiet for long.

A slew of bank robberies is terrorizing the city. And when Professor Farnum, the ringmaster of the museum's now immensely popular flea circus, is charged with murder, the search for the real killer uncovers a plot much bigger than any individual crime-a plot that can only be the work of Nicholas Rattigan.