The Salvager's Quest and The Ghost of the Mountains -- Lucy Hawkins, Paperback

Stella and Dot are two sisters embroiled in an exciting quest to save endangered animals on Earth and bring them to the mysterious Planet Beatrice, where woolly mammoths roam and children make the rules.

This time Stella discovers that humans and animals aren't the only inhabitants of Planet Beatrice when she wanders deep underground into the caves of Neanderthals!

As tensions between the Neanderthals and the children escalate, the sisters are sent on a mission to the Himalayas of Nepal to rescue Snow Leopards. But will any of them be safe back on Planet Beatrice?