When Cammie Morgan enrolled at the Gallagher Academy, she knew she was preparing for the dangerous life of a spy. What she didn't know was that the serious, real-life danger would start during her junior year of high school. But that's exactly what happened two months ago when Cammie faced off against an ancient terrorist organization dead set on kidnapping her.

Now the danger follows her everywhere, and even Cammie "The Chameleon" can't hide.  When a terrifying encounter in London reveals that one of her most-trusted allies is actually a rogue double-agent, Cammie no longer knows if she can trust her classmates, her teachers-or even her own heart. 

In this fourth installment of the New York Times best-selling series, the Gallagher Girls must hack, spy, steal, and lie their way to the truth as they go searching for answers, recognizing that the key to Cammie's future may lie deep in the past.