Dr. Marsha Roo and her crew are living in Australia teaching healthy habits to the other animals in their town. But she turns into Doctoroo! to help solve mysteries all over the world! In this book, Dr. Marsha and her friends help Hilda the Hippo, a famous Opera singer, find out why she is so sick. Will they solve the mystery and help Hilda get better before the Queen of England arrives to watch Hilda perform? Find out in this book along with germ fighting tips!