LONG AGO, when Nim was a baby, she’d had both a mother and a dad. Then one day, her mother had decided to investigate the contents of a blue whale’s stomach. It was an interesting experiment that no one had done for thousands of years, and Nim’s dad, Jack, said that it would have been all right, it should have been safe – but the Troppo Tourists came to make a film of it, shouting and racing their huge pink-and-purple boat around Nim’s mother and the whale. The whale panicked and dived, so deep that no one ever knew where or when he came back up again.

Nim’s mother never came back up at all.

So Jack packed his baby onto his boat and sailed round and round the world – and finally, when the baby had grown into a very little girl, he found the perfect island where he could do his science and Nim could grow, wild and free like the animals they lived with.

The island had white shell beaches, pale gold sand and tumbled black rocks. It had a fiery mountain with green rainforest on the high slopes and grasslands at the bottom. There was a pool of fresh water to drink, a waterfall to slide down and a hidden hollow where the grasslands met the beach. That’s where Jack built their hut.

Best of all there was a maze of reef guarding the island from everything but the smallest boats, because Jack and Nim didn’t want the Troppo Tourists or anyone else to find their island. But one day, Jack and his boat got lost in a storm – and Nim’s email friend, Alex Rover, the most famous and cowardly adventure writer in the whole world, came to rescue Nim.

And then Nim’s most secret wish came true: Jack came floating back, and Alex stayed.