The children burst into the foyer and spotted Song standing with the Chalmers and Peppers.

‘That concert was far more exciting than anyone expected,’ Song said. ‘Your father will be disappointed to have missed it – poor man is full of the flu.’ Everyone had been glad to hear he’d stayed away as flu in the height of a Sydney summer was not what anyone wanted.

Curtis’s father ruffled the boy’s sandy hair and beamed with pride. ‘I didn’t know we had a secret agent in the family. Well done, mate – nothing better than seeing corruption dealt with in a swift and timely manner. I’m intrigued as to how you came by that evidence.’

‘I hope you all said goodbye to Mr Thacker because you won’t be seeing him anytime soon,’ Dash said. He’d just heard via one of his contacts on the school council that the removalists would have the man’s office packed up before he left the Opera House.

Kensy couldn’t help noticing that Tinsley Chalmers was still looking anxious. The woman had glanced at her phone at least a half-dozen times, as if she were waiting for an important call. But it was her husband’s phone that rang again. This time he took himself out of the group to answer it.

‘Are you serious?’ Dash said, much louder than he’d intended. Max took a backwards step to better hear the conversation. ‘What do you mean the transporter hasn’t arrived? Have you tried Lucy? She always picks up.’

At the mention of the woman’s name, Tinsley Chalmers stiffened. She looked at her phone again and seemed to be reading a message on the screen.

‘Those vaccines need to get out tonight or we’ll miss the connections. Right, make sure everything is up from the lab and have the Dalefield gate opened so I can drive straight in.’

Max felt as though he’d been punched in the stomach by the heavyweight champion of the world. The words ‘Dalefield’ and ‘lab’ in the same sentence just took on a whole new significance.

‘I’ll leave in ten minutes, but don’t expect to see me for a couple of hours,’ the man said.

From the expression on her brother’s face, Kensy immediately knew that something was up and it was serious.

Dash Chalmers walked back to the group. ‘Sorry, darling, I’ve got to go to the farm – there’s been a break-in and the police need me to see if there’s anything missing.’

‘I’ll come with you, Dad,’ Van offered.

‘No,’ Tinsley snapped, startling everyone. ‘I have a surprise for the children this afternoon. What a pity you have to go. I was looking forward to all of us doing something together.’

‘What is it?’ Ellery asked.

‘If I told you, it wouldn’t be a surprise, sweetheart,’ Tinsley said, and looked at her watch. She needed to get the children home and changed quick smart. ‘Can you drop us off on your way?’ she asked Dash.

‘What? Just get a taxi,’ the man said. ‘See you later, kids, and well done – although you are a bunch of losers.’ Dash chuckled and hurried away.

‘We can take you,’ Song offered.

But Max had other ideas.

He walked over and spoke to the butler quietly. ‘Can Kensy and I have a look around the shops? We want to get something special for Granny and Mum and Dad.’ He mouthed the last part of the sentence so no one else could hear.

Song grinned. ‘I will take Mrs Chalmers and the children home and you can call me if you want a lift. Although perhaps you are both a bit overdressed for a shopping expedition.’

Max shook his head. ‘That’s all right. We might get some extra-special attention.’

‘What are we doing?’ Kensy whispered.

‘I’ll tell you on the way,’ her brother said.

‘Can’t we go home and get changed?’ she asked, feeling horribly self-conscious.

Max shook his head. ‘There’s no time.’

The Peppers were staying to have lunch at one of the restaurants along the concourse. Curtis gave a reluctant wave as the rest of the group walked to the entrance of the car park, which, like the Opera House it serviced, was something of an engineering masterpiece, spiralling into the earth in two directions like a double helix beneath the botanic gardens.

‘We’ll see you later,’ Kensy said.

‘Why don’t you come over for a swim after Mum’s surprise?’ Van suggested.

‘That would be great, thanks,’ Max said.

But there was no way Kensy was going around there unless it was absolutely necessary. She was stunned when Tinsley Chalmers rushed over and gave her then Max a huge hug.

‘Great job, kids – you were all wonderful today,’ the woman said, glassy-eyed. ‘Come on, Van, Ellery, we need to get home.’

And with that she hurried down the tunnel into the car park with Song leading the way.

As the train pulled into the platform, Kensy glanced at the information board.

‘I don’t see why we couldn’t just steal a car,’ she whispered. ‘It’d be much faster than this.’

The children hopped on and found a seat at the back of the carriage, away from the other commuters.

‘Are you sure that’s what he said?’ Kensy asked.

Max nodded. ‘We have to go – what if Mum and Dad have got it wrong and they’re right here? Even if we’re wrong, at least we’ll know for sure. You did say that Nick was unloading boxes of chemicals last weekend – there very well could be a lab in that shed.’

‘Why didn’t you tell Song? He could have driven us,’ Kensy said.

Max was beginning to wonder the same thing, but it was too late now.

The twins sat side by side, deep in thought. The enormity of the situation was almost overwhelming. The train rolled in and out of stations, the clack of the wheels on the tracks a welcome distraction.

‘I’m starving, Max,’ Kensy complained. She could hear her stomach grumbling and wished they’d thought to get something to eat before they’d hopped on the train.

‘I’ll go and see if there’s anything further back,’ Max said, hoping for a dining car. But when he returned, he brought more than a bag of chips and bottle of water with him.

‘Curtis, what are you doing here?’ Kensy gasped.

The boy smiled and shrugged.

‘You can’t be here – you have to get off at the next station and go back to your parents. They’ll be worried sick about you,’ Kensy said.

Curtis’s eyes dropped to the floor. ‘Sorry, I just thought maybe I could help with whatever you’re doing because you’re clearly not shopping for a present for your grandmother and I thought your mother was dead.’

‘Your ears really are like radars,’ Max said.

‘No, we’re not,’ Kensy admitted, ‘and that’s why you have to go back.’

Curtis sat down opposite them and pulled a sandwich from his backpack, breaking the half in two and passing it to Kensy.

‘How did you even get away from your parents? You were all going to have lunch, weren’t you?’ Kensy asked with her mouth full.

‘Yes, but then I saw you two walking ahead of us. I told Mum and Dad you’d invited me to go with you and they said it was fine,’ Curtis said. ‘They’re so happy we’re friends. It’s just that, you know, Wentworth Grammar hasn’t always been the easiest place to find my tribe and you guys are awesome.’

Now Kensy felt mean. Max looked at his sister and tugged at his left ear.

‘Okay,’ Kensy relented, ‘you can come with us, but you have to do everything we say without question.’

The lad crossed his heart with his right hand. ‘I promise I’ll be helpful.’

‘And if the situation turns dangerous, I want you to get out of the way, okay?’ Max said.

Curtis bit his lip and nodded. He had no idea what was going on, but this was fast turning out to be the most exhilarating day of his life.