About the Book: United We Spy by Ally Carter is the sixth and final book in the bestselling Gallagher Girls YA spy series, following Cammie Morgan and her friends on their most dangerous mission yet. Armed with the truth behind an ancient criminal organisation, the girls must use their espionage skills, intelligence, courage, and teamwork to protect their sisterhood and save the world. Filled with action, mystery, adventure, friendship, and romance, this thrilling finale is perfect for fans of XO, Kitty and young adult spy fiction.