The last thing Cammie Morgan remembers is leaving the Gallagher Academy to protect her friends and family from the Circle of Cavan - an ancient terrorist organisation that has been hunting her for over a year. Then Cammie wakes up in an Alpine convent and discovers that months have passed. Her memory is a black hole, and the only traces of Cammie's summer holiday are the bruises on her body and dirt under her nails. All she wants is to go home, but once she returns to school, Cammie realises that even the Gallagher Academy holds more questions than answers. Now, Cammie, her friends, and mysterious spy - guy Zach will face their most difficult challenge yet. With only their training to guide them, the group must travel to the other side of the world, hoping to piece together the clues that Cammie left behind. But the Circle is hot on their trail and will stop at nothing to prevent Cammie from remembering what she did last summer.