‘Ah, that probably explains it,’ she said. ‘You’ve taught it that a movement of the hand means that something is expected of it. But its problem is that it sees all hand movements as a command. You were both in the pool when it disappeared off to do this, right?’ We nodded. ‘Then I suspect that when you were swimming, the dog watched your hand movements in the water and thought it was supposed to obey whatever that command meant. I just don’t know why it would interpret it as a signal to destroy.’

A light went on over my head, but apparently it had also gone on over Aiden’s. He explained to Mum how he’d trained Z to grab an object by pointing a finger and the verbal command ‘Go’. He also confessed to the dog biting me at this command.

‘You hurt your sister, Aiden?’ Suddenly, judging by her tone of voice, I thought she would go mental after all. ‘I can’t believe you’d be so irresponsible. What on earth were you thinking?’

‘It was an accident, Mum,’ I said. ‘Zorro was supposed to grab me, but I guess he didn’t know his own strength. It wasn’t Aiden’s fault.’

‘I’m not so sure about that,’ Mum replied. ‘Not so sure at all. Anyway, I believe that’s the explanation for the ripping up in your bedroom. The dog thought you’d instructed it to do that. It was just being obedient.’

‘I didn’t say the “Go”,’ said Aiden. ‘And Zorro is a he, not an it.’

‘I’m pleased you find it so convincing,’ said Mum. ‘But the dog is a machine. Never forget that. Anyway, the algorithm responsible for its learning obviously decided that part of the command wasn’t necessary. I told you, it learns for itself and, like any real dog, or person for that matter, sometimes its learning is faulty and mistakes are made. Having said all that …’

Mum cocked her head and looked at Z. He was still on Aiden’s bed, but now he was lying, head resting on his front paws and looking up at us with those big brown eyes. It was breathtakingly adorable, more so because of the mess around him. I’m sorry, he seemed to be saying. I don’t know what I’ve done wrong, but I’m sorry. I was with Aiden on this. Z might be a machine, but he was a real dog as far as we were concerned.

‘What?’ asked Aiden.

‘I put a limiter in its behaviour algorithm,’ Mum said, though it was more like she was talking to herself. ‘It shouldn’t be able to override that, no matter the training you give it and the learning it does. I must have made a mistake somewhere.’