Thea Stilton and the Mountain of Fire (Thea Stilton #2)

Thea's friends the Thea Sisters take off for 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 mouselings set off on a tour of the whole country to find out. It's a truly memorable outback adventure.