ALL THAT FIRST DAY alone Nim did the things that she did when Jack was home. Sometimes she even forgot that he wasn’t just somewhere else on the island, measuring the bubbles at the Hissing Stones or counting eggs in a kittywake’s nest.

But when she went to bed, the wind began to blow.

It had been the tiniest breeze as she sat on the beach to watch the sun go down and wait for the phone to ring; the barest stirring of the palms as Jack said hello.

‘Did you find interesting plankton?’ she asked.

‘Millions,’ said Jack. ‘Trillions. And some greedy birds who thought I was fishing.’

‘Far-away birds?’

‘Home birds. The big one you call Galileo swooped me in case my microscope was a fish. I told him to go home and bother you.’

Nim laughed. ‘He did! I only caught one fish all afternoon – and he snitched it right out of my hand! So I gave up and read on Selkie’s Rock.’

‘Good book?’

‘Mountain Madness. You said it was your very favourite, remember?’

‘So I did,’ said Jack.

‘Because it’s exciting?’

‘I liked the people in it,’ said Jack. ‘I felt as if the Hero could be my friend.’

‘It’d be funny having a friend that could talk.’

‘Honk, whuffle, grunt,’ said Jack in his best sea lion voice. ‘Selkie can talk! She’s just not very good at telling stories.’

Nim patted Selkie in case that hurt her feelings.

‘Don’t forget to check the email,’ Jack went on. ‘Say I’ll answer in a few days. Unless it’s the Troppo Tourists – I’d rather meet six hungry sharks than that pink-and-purple boat!’

‘I’d rather meet a cyclone at sea!’

‘I’d rather jump in the fire from Fire Mountain … or talk to Nim when she hasn’t had enough sleep!’ said Jack. ‘Don’t stay up too late reading!’

So Nim blew iguana kisses into the phone, and went back to the hut, and the breeze flicked her hair and was cool against her cheek.

It was already dark in the hut, and when she checked the email, even though she didn’t know anyone in the wide, wide world who might send her a letter, it made her lonely to see ‘No Messages’ in the email box on the screen.

‘Goodnight, Selkie!’ Nim called. ‘Goodnight, Fred!’

Fred was already asleep in his little rock cave beside the hut, but there was a quiet honk from Selkie’s Rock.

Nim lay down on her mat with her torch and her book.

The waves rumbled onto the reef and mumbled across the sand. The breeze whistled through the cracks in the walls, and there was no comforting noise of Jack humming to himself or turning pages.

Nim felt excited and brave and a tiny bit afraid, but the second chapter of Mountain Madness was even more exciting than the first, and she thought about the Hero till she went to sleep.

The wind grew stronger. It howled at the door and screamed through the windows; it laughed at Nim because Jack wasn’t there, and she didn’t know if it was just teasing her or was going to grow to a tree-throwing, hut-smashing storm.

She switched on the torch and crept outside.

The clouds were scudding across the moon; the stars had disappeared and there was a lashing of rain. Nim stumbled and nearly dropped her torch, but she could see Selkie’s shape, darker than the night, and heard her bark, deeper than the wind.

Selkie nuzzled Nim’s shoulder and curled tight around her. The wind passed, the tail of a storm roaring out to sea, and Nim was snug in her sea lion shelter, breathing the warm smell of fur.

Next morning, coconuts were scattered over the beach and the hut had a dent in the roof, but the solar panel was safe and the satellite dish, sitting above the hut like a fat white coconut, was still waiting for messages to bounce across the world and into Jack’s email.

Inside, the hut was gritty with sand. Mountain Madness had blown open, and a piece of newspaper Jack had used as a bookmark was stuck against a wall. Nim tucked it back inside the cover, and started cleaning the hut.

She shook her sleeping mat outside the door, swept out the sand, and used a scrap of old T-shirt to dust the laptop and Jack’s science stuff, her polished driftwood, a threaded wreath of shells and the picture of her mother.

Her mother had bright, clever eyes and a wide, funny smile; she looked happy-excited because it was the morning she went diving to investigate the contents of the blue whale’s stomach.

Nim put the photo back on the shelf.

She put her empty water bottles into her wagon and whistled for Fred – Fred liked going wherever Nim went, especially places where Selkie couldn’t follow. He curled spikily around her neck and they towed the wagon across the grassland, up to the tangled vines and ferns of rainforest.

At the edge of the rainforest was a wide rock pool with a waterfall tumbling into it, and on the other side of the pool was the garden.

There were plants to prop up that had toppled over in the wind, weeds to pull and strawberries to nibble, and a huge bunch of bananas just green enough to pick.

Nim liked bananas, but what she liked even better was swinging Jack’s machete. It was shiny and sharp and made her feel like a pirate.

‘Aargh, me hearties!’ she shouted, and chopped down the bunch.

She dragged them to the shed and hooked them to a rope looping over a beam in the roof.

‘I’m swinging the bananas!’ And she grabbed the rope just above her head. Fred jumped and clung to the end with his claws. Swinging hard and heavy, they hoisted the bananas up to the roof to ripen.

It would have been easier if Selkie had helped, but sea lions aren’t much good at swinging on ropes.

Nim put the machete away. ‘Are you hot?’

Fred knew what she was thinking. He raced her up the path to the top of the waterfall.

Over thousands of years, the water trickling down the mountain had worn away the steep black rocks to make a curving slide. It was perfect for whooshing a girl and an iguana over bumps and dips and splashing them into the pool at the bottom.

Nim and Fred ran up and slid down until it was time for lunch. Then Nim picked up a tomato and an avocado that had fallen off in the wind, and weeded quickly around the peas.

‘They’ll be ready tomorrow,’ she told Fred.

But Fred didn’t like peas, and he was getting bored. He started chewing leaves and spitting them out.

‘I won’t bring you up to the garden again!’ Nim said sternly. Fred spat out the last bit of pea leaf and crawled into the wagon for a wild ride down the hill.

THAT NIGHT, when Nim sat on the rocks with the phone and watched the sun sink red into the waters, Jack didn’t call. She pressed his number but his phone didn’t ring and he didn’t answer.

She checked the email and there was nothing there either.

Nightmare pictures sneaked into Nim’s head: upside-down boats, sinking boats, boats sailing off into the distance with fallen-off people swimming behind…

She pushed the scenes away angrily. Jack was busy. He was concentrating on his plankton and didn’t know what time it was – like when he was doing science things at home and forgot to eat.

She picked up her book, and soon she wasn’t Nim any more, she was a strong brave Hero scrambling up a cliff, she was swinging across a chasm, reaching for the other side… and rubbing her aching eyes, looking up to see that the hut was dark and her torch beam was fading into the night. But she stayed being a Hero till she went to sleep, because tonight she liked it better than being Nim.