Having met Joe and Jeanie Bravo in The Day of the Dragonfly, their adventures continue in Myrtle Mountain when they travel separately to the tiny European country of Libelulonia to join an expedition to the Malagashi Mountains, organised by their dear friend, Dougie McBride Adjabanko, brother to the King of Libelulonia and current Minister for the Environment. Initially, Jeanie is delighted to make friends with the glamorous Maude on the plane, but when she sees how Maude manages to wangle her way onto their expedition and into the affections of Dougie, Jeanie rapidly changes her mind, and begins to wonder what exactly Maude is up to? Joe, having travelled to Libelulonia overland by motorbike, meets with the young Hollywood actress, Elizabeth Knight, along the way, never realising that he has a lot more in common with her than he could ever have imagined. The members of the expedition are invited to stay at the ancient monastery of San Fiacre in the Malagashi Mountains ("malagashi" being the Libelulonian for "myrtle"). However, an expedition that should have been fun and scientific turns nasty when an irreplaceable old book of medicinal plants is stolen from the monastery library and the children's mother is accused of the theft. Jeanie, suspicious of Maude and her relationship to one of the young monks, enlists the help of Ivo, the son of one of the expedition's scientists, to find the book and clear her mother's name. Ivo not only proves to be the ideal partner in adventure, but awakens feelings in Jeanie that she has never encountered before!