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. Between classes, friendships, crushes, and some bizarre mysteries to solve, they find life to be a never-ending adventure!

Colette, Violet, Pamela, Nicky, and Paulina are working on a historical restoration when they learn about an ancient Viking vessel that sank off the shore of Whale Island. Rumor has it that the ship is full of treasure, and what's worse, some shadowy figure is plotting to steal it! If Mouseford's best investigative journalists can't crack this case, Whale Island will lose one of its most important cultural artifacts before it's even found.