Sirena, Lyla and Nixie resurfaced inside the Moon Pool.

'This is disastrous,' Lyla told them, 'We can't have a thirteen-year-old merman running around. Anyone could find out!'

'At least Cam showed some foresight, bringing him here,' Nixie pointed out, 'It could have been way worse. Maybe we can still trust him,'

'We'll see when he shows up,' Lyla replied, 'He might have other plans that we don't know yet.'

Nixie grimaced as Zac broke the surface, still in diving gear.

'No sign yet?' he asked. The girls shook their heads and he sighed. 'I'll go and ask if the bluefins have seen him,' he told them, 'I shouldn't be too long,'

'Look at you, all suited up,' Nixie smirked at him, 'Bet you're missing your tail now, land-boy,'

'Nixie, now's not the time,' Sirena told her. Zac pushed the mouthpiece in between his teeth and sunk below the water again, swimming out through the underwater entrance.

*~X~*

'We haven't seen him,' Tory told Zac, 'But we'll be sure to let you know when we do. Can I ask-?'

'We switched powers when I touched the necklace,' Zac explained quickly, gesturing to the diving gear, 'Now, he's a merman and I'm...'

'Human,' Tory nodded, 'This necklace, can you describe it?'

'Better yet, did it look like this?' Loren asked, holding out a piece of paper. Zac took one look at the picture and nodded.

'That's definitely it,' he told them, then noticed the glance they exchanged, 'Why, is that a bad thing?'

'It's a very bad thing,' Tory replied, 'looking around, furtively before lowering his voice, 'That necklace takes a merperson's powers. If the wearer is not already merfolk, they will be after they take their first victim's powers. After that, it absorbs power from all merfolk within a certain distance.'

'Like the Trident?'

'Worse than the Trident,' Tory looked at his pod, who were engaged in various activities, 'Zac, you are not as badly affected by it because you're a natural-born human. Natural-born merfolk, however... it will drain them until they die,'

Zac stared at Tory, 'What about if we took it to the source of the mermaids' power?'

'It will drain the energy from that, too,' Tory replied sadly, 'And in doing so, drain every merperson connected with it. Keep it away from your source, at all costs,'

*~X~*

'You can't leave me behind!' Tyson cried, 'That's my twin down there,'

'I only have one tank,' Cam replied, 'There's not enough for three of us,'

'Only two of us need it!'

'If this works, three of us will need it on the way back out,' Cam pointed out, 'Tyson, I know you want to come, but-'

He was interrupted as Zac surfaced alongside them, spitting out his mouthpiece. 'Cam! Where's Caleb?'

'He was following us,' Cam replied crouching in the boat as he took in Zac's wetsuit and diving gear, 'So it's true? He took your powers?'

'All of them,' Zac replied, 'We can't let him go into the Moon Pool,'

'Why not?'

'The necklace was a merman weapon,' Zac explained, 'If we take it into the Moon Pool, it'll destroy it and kill all the mermaids connected with it.'

'Just the mermaids?' Cam asked, 'What about you?'

Zac hesitated, 'I don't know. But Tory says once it's started, it doesn't stop, even if it leaves the Moon Pool. And it affects all merfolk, both natural-born and transformed.'

'So we stop him from going into the Moon Pool,' Cam nodded, 'I'll stay here, and stop him when he shows up,'

'I'll wait at the entrance, in case he's already gone there,' Zac replied, 'I'll warn the mermaids, too,'

*~X~*

Caleb slowed down, admiring his tail. He had travelled incredibly fast through the water, and was already at the reef. He kicked his tail lazily, moving towards the surface. Mako Island was nearby, and he could see a boat already anchored close to the shore. There was no way that was Cam - he had left Cam in his wake when they'd left the shore, and he knew he moved faster than a boat.

Caleb flipped and dove towards the reef, exploring the rocky corals. He sensed something zipping around him fast, and thought it might be some sort of fish. Looking up, he realised he was very mistaken.

The first thing that struck him was her red hair, a bright red that matched one of the corals he had just been observing. Her tail was a bright purple colour, with side fins, and the lower half of it looked like it was covered in exotic weeds, partially hiding her red flukes.

She hovered in the water in front of him, bright green eyes searching him carefully. They widened when they spotted the necklace, and she pointed at it. Caleb looked down, then back at her. She mimed taking it off, but he shook his head. If she wanted it for herself, she would have to fight him for it.

She opened her mouth, emitting a loud shriek that seemed to shake the water around her. Caleb flew backwards, hitting the sandy floor with a soft thump, and looked up in time to see her turn away from him, flipping her tail once before disappearing in a trail of bubbles.

Caleb floated up, looking around. There was no sign of her.

*~X~*

Sirena, Lyla and Nixie whirled around as an unfamiliar mermaid appeared, breaking the surface.

'What were you thinking, letting the mermen stay?' she demanded. Lyla recognised her almost instantly as the reef mermaid they had rescued a few days ago.

'Who are you?'

'That doesn't matter,' the reef mermaid replied, 'I just saw one of them on the reef, with one of their greatest weapons. It looked like he was heading here,'

'We made peace with the pod,' Sirena stated, 'They wouldn't attack us. They don't even know where the entrance is,'

'The one I saw looked very young,' the mermaid replied, looking at each of the girls in turn, 'He was wearing a necklace, with a moon stone in it - I could feel it draining me even before I saw him,'

'Wait, draining you?' Nixie asked. The reef mermaid looked at her.

'Yes, do you not know the story about Neptune's Necklace?' she asked incredulously. Nixie, Sirena and Lyla exchanged glances, before shaking their heads. The mermaid sighed heavily.

'There were two great merman weapons in the ancient war,' she explained, 'The Trident, which has been destroyed-'

'How do you know that?'

'I felt it, just like those mermen felt your friend using it,' she replied brusquely, 'The other weapon was the necklace. It was designed, like the Trident, to feed off the mermaids' power, but only when it was being worn. Back then, it turned mermaids into land-people when it removed all their powers, and that's why mermen are so much stronger than us,'

'"Back then"?'

'Now, because it was locked away for years,' the mermaid looked at the girls, 'It won't just turn you to a land person. It will keep draining your energy until you're dead,'

The girls looked at each other. 'Cam is bringing it here,' Lyla said, 'We can destroy it then,'

'It cannot be destroyed,' the reef mermaid told them, 'The only way to stop it draining power is for a mermaid to agree to wear it - it will permanently render her a land-person, but it will keep mermaids everywhere safe,'

'How did it get here?' Nixie asked. The reef mermaid looked at her, before dropping her eyes.

'That doesn't matter. If you bring it here, it will drain the Moon Pool, and all the mermaids associated with it - including your old pod,' she turned back to Lyla, 'You have to stop it from getting in here.'

'You're not going to help us?' Sirena asked, 'Doesn't it affect you, too?'

The reef mermaid looked at her. 'Stop the necklace coming here,' she replied, 'And get it off him. I'll take care of it from there,'

Before they could say anything, she had turned and dived away, through the opening.