The sixth and final book in the million copy selling Gallagher Girls series set at an elite boarding school for spies. Perfect for fans of XO, Kitty. What is a Gallagher Girl? She's a genius, a scientist, a heroine, a spy . . . a Gallagher Girl is whatever she wants to be. Cammie Morgan is about to take on her final and most dangerous mission at Gallagher Academy. Armed with the truth about why she's being hunted by an ancient criminal organisation, Carrie and her friends must track down its elusive members to save their sisterhood - and the world. But will they survive to see graduation?