When Geronimo's sister, Thea, is invited to teach a journalism class at a college, she has no idea that she's going to help solve a mystery. But when a mouse disappears, it's up to Thea and five of her best students to find out what happened.

The second adventure in this hot new series starring Geronimo's sister, Thea! Thea's friends the Thea Sisters head to Australia to solve a mystery. A flock of sheep at Nicky's family's ranch is losing all its wool, and the ranch depends on the wool to stay afloat! Maybe the sheep's cure lies in an Aboriginal medicine containing a strange root. The five girls set off on a tour of the whole country to find out. It's a truly memorable outback adventure. Readers will love following the clues to help Thea's friends solve the mystery.

Violet has been chosen to play in the orchestra for a production of Romeo and Juliet in London! The mouselets begin to notice strange things happening during rehearsals. Someone is trying to sabotage the production. Can the Sisters uncover the phantom before the show is ruined?

The Thea Sisters are invited to the Festival of Time in Germany! They arrive in the Black Forest and find that a famouse clock has been stolen. The mouselets are on the case. Can they find the thief and return the clock before time runs out?

Join Thea Stilton and the Thea Sisters on an adventure packed with mystery and friendship! The Thea Sisters help their friend Beatrice prepare for the Summer Olympics!

Join Thea Stilton and the Thea Sisters on an adventure packed with mystery and friendship! The Thea Sisters are off to save the rainforest in Malaysia.

The Thea Sisters are going to New Zealand! Their new friend Charlotte wants to show them the sights, and introduce them to Didi, a skeleton of a bird that went extinct many years ago. But when they get to the mouseum, Didi has gone missing! Can they find the stolen skeleton before it is too late?

It's election time at Ratford College and the candidates from the Lizard and Gecko student clubs face some challenges if they want to get elected president. Certainly not helping matters is the arrival of a mysterious black ship off the shores of the island . . . and it's trying to pollute the beach! The girls must use all their investigative skills to root out the connection between the ship and the campaign. The fates of the election and their beautiful island home is at stake!

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.

Thea Stilton sends Colette, Paulina, Violet, Pamela, and Nicky on a school project exploring in and around Whale Island in search of treasure. When a bad storm interrupts their scavenger hunt, separated, the Thea Sisters must rely on their individual knowledge and skills to make it through the storm and realize the true treasure is being themselves!

There's going to be a musical at Mouseford, and the Students can't stop squeaking about it! Everyone wants a role, but the auditions won't be easy. Plus, sneaky Ruby Flashyfur has some tricks up her sleeve.

The Most Famouse band on the Mouse Island, the Ratstreet Boys, is performing at Mouseford Academy! The band's producer, Mark Mousington, is auditioning student bands as the opening act. Can the Thea Sisters win the spot as the opening band?

Anna Winmouse, the fabumouse editor-in-chief of Cosmouse magazine, is renting Cheddarton House, a cottage that overlooks Whale Island's Seashell Beach. She's trying to get away from the media for a while, but it hasn't been easy. Can the Thea Sisters help her keep her visit to Whale Island a secret?

Using the clues found in Aurora Beatrix Lane's travel diary, the Thea Sisters continue their search for the seven lost treasures; and the object this time is the Ring of Eternal Love, a journey that begins in Verona, Italy, with the story of Romeo and Juliet and takes them around the world.