SELKIE AND FRED both knew lots of tricks, but they only did them when they wanted to. It was hard for Nim to make them understand that the only way they were going to outsmart the Professor was to do the tricks Nim wanted, when she asked.

And the Professor was watching. He was in a very bad mood because one of the baby spider monkeys had bitten him while he was giving his lecture.

Nim didn’t want him to be angry at Selkie, too, so first she fed the birds, chirping quietly to them in their own languages.

‘If you make bird noises, they’ll never learn to talk!’ the Professor snapped. ‘Teach them “Pretty Polly!” That’s what people pay … are interested in.’

Without waiting for an answer, he stomped out the door. Nim was alone with the animals.

She clucked to the doves once more and rushed to open Selkie’s cage. Selkie whuffled and sniffed her all over, as if Nim was the one who’d been seal-napped and locked up.

‘We’ll get home somehow,’ Nim told her. ‘Because even if Alex doesn’t like me any more, I know she’ll help us get back.’

‘Anyway,’ she added, ‘the important thing is to escape. We’ve got five days to get ready.’

She looked at Selkie’s little cage and the cloudy tub of water, and five days seemed for ever.

‘If I could just get you into a pool,’ she said, ‘it wouldn’t be so bad.’

Very quietly, she turned the door handle. It wasn’t locked. She opened it a crack and peered down the hall.

The Professor was coming.

Nim shut the door quickly. She hugged Selkie hard and just for a minute she thought she was going to cry – but that would upset Selkie more than being in a cage.

And it was crying that got us into this mess in the first place! Nim thought, which suddenly seemed so silly she almost laughed – except now the Professor was in the room again, so instead she clapped.

‘Fantastic!’ she said, as if Selkie had just done the most wonderful trick in the world.

Then she added quickly, in case the Professor asked to see it, ‘That’s enough training for today.’

The Professor grunted. ‘Okay, kid, get the rest of those animals fed and cleaned out. If you do a good job I’ll let you do some more training in the morning.’

‘Thank you,’ Nim said politely, working as slowly and carefully as she could, because every minute she was here was a minute Selkie wasn’t locked in her cage alone.

Suddenly, she spotted a key hanging behind the door. It looked just like the Professor’s, but she’d seen him drop his into his pocket. This one had to be a spare – and if it was a spare, he might not notice if it was missing.

So Nim brushed the rotten fruit and droppings out of the monkeys’ cage, put in clean water and not-quite-rotten fruit and murmured quietly to them, trying not to let them feel how sad and angry she was to see them there.

Finally she put Selkie back in her cage, sitting beside her for a long moment to rub her head with love and cool water.

‘Just remember,’ the Professor said, with his sneering smile, ‘this place is our little secret. The Foundation’s work is very important – much too important for most people to understand. I don’t ever want to hear you talking about the animals down here.

‘So, my little stowaway friend, just keep your mouth shut and everyone will be happy: I’ll get a fat stack of money, the animals will get lovely new homes that appreciate how intelligent, unique and interesting they are – and you and your mum can stay out of jail.’

Nim swallowed hard, and nodded. He wanted her to be afraid, and she was. More afraid than she’d ever been. She was so afraid that the Professor knew he didn’t have to worry about her at all. He sat calmly down in his chair in the corner, opened a can of drink and started to read his newspaper.

‘I’ll come back in the morning,’ Nim whispered.

The Professor grunted and turned a page.

Nim backed to the door – and as she waved goodbye to Selkie, snatched the key off its hook.