Katy has recently adopted a Sumatran tiger – the most endangered tiger in the world. The tiger lives on an island in Indonesia, and she’d love to go on an adventure to find it. While playing at the back of Luca’s garden, the garden magically transforms into the Sumatran jungle. But no matter how hard they all look, there’s no sign of the tiger anywhere. They learn from the other creatures that the tiger hasn’t been seen in weeks. As they navigate river rapids and a close encounter with a venomous snake, Luca and the girls learn about the threats to endangered species. Can the four friends and Thunder help find the last tiger?