Geronimo isn't the only world-famouse adventuring journalist from New Mouse City; introducing his fabulous sister, Thea! The Thea Sisters are five fun, lively students at Mouseford Academy on Whale Island, who want to be real, live journalists just like their hero, Thea Stilton.

Like most girls their age, between classes and friendships, love and small fits of jealousy, they're finding college life is really exciting! But unlike most girls their age, the Thea Sisters have an unusual responsibility; the delicate ecology of their beautiful island home is under threat, and only their investigative reporting can put a stop to it before it's too late!