The Thea Sisters embark on another adventure in Geronimo Stilton - Thea Stilton And The Ghost Of The Shipwreck. The story is narrated by Thea Stilton, Geronimo’s sister. In this book, the Thea Sisters go in search of a precious diamond called Jasmine’s Heart, which was lost in a shipwreck. The adventure starts during a marine biology session at Mouseford Academy, where they learn about the mysterious shipwreck and the diamond. They go on a mission to find the diamond, and investigate further when their teacher, Professor Van Kraken goes missing. The story continues with the Thea Sisters visiting China next, to recover another lost treasure.