With the kidnappers gone, the fastest way to find Kensy and Autumn was through the house. Max turned the handle of the front door and was almost bowled over by the girls on their way out.

‘Her name is Claudia Montez. She’s in charge of production for a new company called Wolf Motors, which must be an offshoot of Wolf Racing, and has a stack of degrees in mechanical engineering and industrial design and pretty much anything else you can think of to do with cars,’ Kensy blurted. ‘If I knew her I’m sure she’d be my idol.’

‘She’s also just been kidnapped,’ Curtis said.

‘We know,’ Autumn replied. ‘We heard them in the house.’

‘Did you see them?’ Max asked.

Autumn shook her head. ‘It was too dark and they were wearing balaclavas.’

‘I thought you were going to send Ferdinand in,’ Max said.

‘I did, but then he got stuck so we went after him,’ Kensy replied. She was nursing the drone in her palm, one of its wings clearly damaged.

‘I’m tracking them,’ Curtis said.

Kensy grinned. ‘Amazing! I could totally hug you right now, Curtis Pepper. But don’t worry, I won’t, because I know you’d die of embarrassment.’

That wasn’t exactly how Curtis felt but perhaps it wasn’t the right time to say he would have been okay with it.

The boy looked at the blip on his watch. It had stopped moving and wasn’t terribly far away.

‘Hiding in plain sight, perhaps?’ Curtis said, showing the screen to Max.

Autumn nodded. ‘What do we do now? We can’t just leave her with those guys.’

‘Dead right we can’t,’ Kensy said.

She was ready to go, but Max bent down to pick up the syringe he’d seen the man drop while bundling Claudia into the van.

‘Don’t touch that,’ Kensy ordered. ‘It’s gross and dangerous.’

‘It’s evidence. I think this is what the guy used to knock Claudia out,’ Max replied.

Curtis pulled a small cylinder from his backpack and took the syringe from Max, depositing it safely inside.

‘What else have you got in there?’ Kensy asked. ‘A DNA scanner? That would come in handy right about now.’

Curtis shook his head. ‘Mrs Vanden Boom won’t give me one of those. Believe me, I’ve tried.’

At the mention of the woman’s name Kensy’s stomach tightened. She hadn’t even thought about the note Max took from Magoo’s study in the past couple of days, nor why Mrs Vanden Boom would be out to get them. Being reminded of it again now made her feel sick.

‘Let’s not talk about her at the moment,’ Kensy said, glancing at her brother. ‘Are we going or not?’

The children nodded. Together, they ran down the road towards the centre of the village. Curtis was in the lead, following the red dot on the map on his watch and hoping that the van stayed put until they got there.

‘How far is it?’ Autumn asked as they jogged along the cobbled streets.

‘I think once we reach the palace with upturned ice-cream cone chimneys, it’s about seven hundred metres,’ Curtis replied.

It didn’t take long for the children to get to the Sintra National Palace, running until they were literally just around the corner from the van.

‘Is it still there?’ Kensy asked, puffing.

‘Yup,’ Curtis replied. He spotted an ancient water fountain on the side of the road and stopped for a quick drink. They were heading towards another palace – the Quinta da Ragaeleira.

‘What are you doing?’ Max whisper-shouted back at him.

‘Coming,’ the boy replied, quickly catching up. ‘According to this, the van should be about one hundred metres away.’

The children charged around the bend and stopped.

‘What?’ Autumn gasped. ‘Where is it?’

Curtis checked his watch. The red dot hadn’t moved, but clearly it was no longer attached to the van.

‘The tracker must have fallen off,’ Kensy said. ‘That’s a disaster. How are we going to find Claudia now? They could have taken her anywhere.’

The children stood outside the ornate gates to the palace, which were locked up tight.

‘We need to find the tracker,’ Max said.

‘I don’t see what difference that’s going to make,’ Kensy replied. ‘We’ve lost them.’

But her brother wasn’t so sure about that.

‘Think about it. If the tracker is out here on the roadway, then fine – we’ve lost them – but if it’s on the other side of those gates, then that’s a different story. The van would have to be inside the grounds for it to fall off there.’

Autumn smiled. ‘That’s great thinking, Max.’

Kensy rolled her eyes. She wished she’d come up with that. ‘Come on then, genius.’ She looked at her brother. ‘Let’s find it.’

The children scanned the roadway and the much trickier cobblestones in the layback right outside the palace entrance. After twenty minutes of searching, they had nothing.

‘We’ll have to go over the gates,’ Max said. There was nothing tricky about them – with their ornate metal curls and relatively low height, scaling them was barely a challenge.

‘No!’ Autumn said. She’d been checking for security cameras and realised that what she initially thought was just the tip of a sculptured stone gatepost was actually concealing a device. She had only just seen the reflection in the light and hoped that no one had been watching them.

She pointed covertly so the others could see what she was talking about.

Max had it covered. He quickly took a piece of chewing gum from a packet in his pocket and popped it into his mouth, then scaled the gatepost before placing the masticated blob on the lens. He checked to make sure there was no camera on the other side.

‘Come on,’ he urged the others to follow him over the gates.

Curtis dropped down and looked at his watch. The blip had suddenly become brighter.

‘It’s here somewhere,’ the boy said, eyes on the ground.

‘There!’ Kensy declared, seconds after she’d landed. She bent down and picked something up, examining it closely before she got a whiff of a smell that caused her to gag. ‘Ew, false alarm,’ Kensy said, throwing it back down and wiping her hands on her pants.

‘Really, Kens, you can’t tell the difference between a tracker and a piece of dog poo?’ Max said with a chuckle.

‘Of course I can,’ Kensy retorted, looking around to see if there was a tap anywhere close by. The stink was awful.

Minutes later, Autumn’s excellent eyesight triumphed once again. She bent down and picked up the tiny black device, holding it out for Curtis to see. ‘Is this it?’

He nodded.

‘So they drove the van inside the gates,’ Max said. ‘That means Claudia could be here somewhere.’ He pointed towards the castle. ‘And the van could be too – there’s a garage over there.’

‘But where, exactly?’ Curtis said, looking around. There were multiple outbuildings and a smaller turret-like construction further up the road – it would take an age to check all of them.

‘We need to split up. We can cover more ground that way,’ Kensy said. The idea of racing around a strange place in the dark was a little disconcerting, particularly after her grandmother had told her about the well in the grounds.

‘Autumn and I will go together,’ Max declared. The girl grinned.

‘Okay, Curtis, looks like it’s you and me then,’ Kensy said.

‘We’ll take the palace and everything further down the hill,’ Max said. ‘You two head up there – near the outbuildings – and keep in touch.’

Thunder grumbled in the distance and a shard of lightning split the sky.

‘Let’s hope we find something before the storm hits,’ Autumn said.