In the mountains that tower over the sleepy town of Pistachio, a secret sect of unlikely assassins live, pray and make apple pies in an abbey surrounded by telescopes. After many years of peace, the guardian nuns turn complacent. When the Reverend Mother suddenly discovers that the crime rate in Pistachio has skyrocketed drastically in recent months, she calls for reinforcements. What she gets instead is a eleven-year-old, excitable and very accident-prone orphan, Ann. As Ann and the formerly peaceful abbey adjust to each other, the crime rate in Pistachio continues to rise and the Reverend Mother sends the youngest member of the order down to Pistachio to investigate. Beginning her foray into secrecy and assassin-like behaviour, Ann soon finds herself up to her elbows in a flood of unusual behaviour around town. Hilarious and heart-warming, join Ann on her unforgettable adventure as she learns the importance of friendship and family and the right way to bake a raspberry crumble while sharpening an arrow.