In this fourth mystery about twelve-year-old Maisie, the young detective must solve a crime for her friend Professor Tobin. The professor travelled all over the world collecting strange and wonderful objects, and the British Museum is opening a special room to house his collection. But before the professor’s donation, a thief steals a valuable Amazonian tribal mask! With just a single feather left behind, Maisie doesn’t have much to go on, but the stakes in her newest case are higher than ever.