Zac carried Rikki into Rita's house, and everyone followed, Sirena running in front so she could open the front door for Zac.

Rita didn't seem to be in the house, so they decided to go to The Grotto. Sure enough, Rita was there. She was stood by the table, looking through some potions. As soon as she heard the bookshelf slide open she turned around.

Zac, with Rikki in his arms, was the first to get there.

"Rita," he panted.

"Zac." Rita put the bottle down. "Who is that?" She motioned to Rikki.

"This is Rikki, and she's in trouble," Zac replied.

"Bring her over here," Rita held her hand out to the sofa.

Zac carried Rikki and gently laid her down as everyone else ran into the grotto.

Rita bent down and felt Rikki's forehead, which was cold. "How long has she been like this?" Rita asked.

"Not long at all," Evie said, shaking her head.

"We wanted to see if she would better on her own," Lyla explained.

Rita stood up straight. "How did this happen?" She asked.

"It was all my fault!!" Mimmi cried. "I made a potion, intended for Erik, but Rikki accident drank it instead!"

Rita looked up at Mimmi. "Erik!?" She asked, extremely surprised.

"Yes, we met him a few days ago, we think it's him who has been stealing the moon stones," Ondina said, her arm around around a sobbing Mimmi.

"He wants to restart the Merman Chamber," Sirena said.

"We also thinks he's trying to eliminate us, one by one," Emma said.

Rita's eyes flickered to Emma. Then Bella, then finally Rikki. "Didn't you say you found four mermaids?"

"Cleo," Lewis said. "She's missing, we think Erik took her."

"He almost got to Bella and Sirena, but we managed to stop him in time."

"And Erik isn't working alone, this time," Lyla told Rita.

"He's working with some girl called Charlotte, who knows all about Cleo, Emma, Bella and Rikki."

"Speaking of Rikki, can you help her?" Bella asked curiously.

"Mimmi, what potions did you use?" Rita pointed to Mimmi.

Mimmi told Rita the potions. Whilst she was doing so, Rita fumbled through her potions, picking some of the colourful bottles up, but putting most of them back.

"I can help her. There is just one ingredient I'll have to get: blue coral."

"Why do you need blue coral?" Ondina questioned Rita.

Rita began. "Blue coral is the only known coral with a skeleton."

Nixie rested her head in her hand. "And you know what because-"

"Because I paid attention in school Nixie," Rita replied.

"So the blue coral?" Evie prompted Rita.

"Yes, the potion in Rikki, of not treated, will cause her a lot of harm."

"How much harm is a lot?" Mimmi asked, shaking slightly.

Rita paused for a moment. "... I'm not sure I should say... But blue coral has a skeleton-"

"You've already said that," Nixie said.

"Shhh!!!" Everyone hushed her.

"For mermaids, blue coral - like a skeleton- gives them strength and structure inside. It will build up Rikki's immune system, and her body will get better."

"Where is the coral?" Zac asked.

"Mako Island," Rita said. "But it's...on the other side."

"In the shark territory?" Lewis asked.

Rita nodded.

"That's too dangerous," Will shook his head.

"But not for mermaids," Emma gave a small smile.

"I'll go," Sirena said at once. "I am the only one who still has a moon ring."

"And she shouldn't go alone," Bella said. "I'll go too."

"Maybe I should go as well?" Zac suggested.

Belle shook her head. "It would be better if less people went."

"But it will be getting late, and you won't be able to make the journey there and back before it's too dark," Rita said.

"We'll be quick," Sirena promised. "If not, we can spend the night at Mako."

"Last time we were at Mako it didn't exactly go well," Nixie said.

"What, and being here was?" Sirena shouted.

Everyone was quite taken back by Sirena's shouting. She rarely got angry.

"Why don't we stay at the café?" Evie said slowly. "I'm sure David would let us. I'll text Carly."

Sirena sighed. "Sorry, I just want Rikki to get better and Cleo to be saved."

"We all do," Lyla said, putting her hand on Sirena's shoulder.

Sirena looked at Rita. "Please can I go find the coral?"

Rita sighed. "You'll have to be quick."

Sirena and Bella smiled.

"We will," Bella promised. "Thank you!!"

Sirens and Bella rushed out of the grotto, and ten seconds later everyone heard the sound of them jumping into Rita's pool.

But Sirena and Bella didn't go to the blue coral. They did, however, go to the white boat that Cleo had seen. There, Sirena and Bella managed to pull themselves up the ladder.

They were greeted by Erik, Charlotte and Dr Denman.

"You took your time," Erik said, steam drying Sirena's and Bella's tails.

"Rita wouldn't let us leave," Sirena said through gritted teeth.

"Where's Cleo?" Bella asked.

"Downstairs, sleeping peacefully," Dr Denman grinned.

Sirena's and Bella's tails disappeared and were replaced with their human legs. Charlotte grabbed Sirena's hands, Erik took Bella's, and they pulled the mermaids up.

"So, my lovely Sirens... What news is there?" Erik asked.

"Rita has told us about blue coral, which will make Rikki better," Bella said.

"Well we can't let that happen," Charlotte said. "The less mermaids in our way, the better."

"Exactly," Bella nodded.

Erik grinned. Sirena and Bella were under his spell, he was in their minds, he could make them say or do anything he pleased!!

"So how do you suggest we stop them?" Dr Denman said.

"Find poisonous coral and enchant it to be blue?" Charlotte shrugged.

"Rita is too smart for that," Sirena shook her head.

"I know," Erik snapped his fingers. "Go get the coral, but don't get enough."

"And then?" Bella asked.

"And then get some of the other mermaids to get more coral tomorrow, and we'll go and...sort them out."

Sirena and Bella looked at each other and grinned.

Everyone said goodbye, and Sirena and Bella jumped into the water, and swam to the blue coral. There were lots of sharks, but Sirena knew that the sharks would only disturb them if they sensed the mermaids were scared.

Sirena and Bella quickly rose to the surface, and Sirena explained this to Bella. They quickly collected some coral and swam back to Rita's.

"We tried to be as quickly as we could," Bella said, Sirena following her.

Everyone was still sat in the grotto.

Rita stood up. "You have the blue coral?"

Sirens and Bella held out the coral they collected. Rita took it, thanked them and walked over to the table with all her potions. Mimmi and Lewis were the first to crowd around, and everyone else joined them.

Rita began working. She had a small wooden bowl in front of her, where she began pouring potions and mixing in seaweeds and magical plants found underwater.

"The blue coral now," Rita ordered after a few moments.

Lyla gathered up all the pieces in a clump on the table and pushed them towards Rita. Rita paused, and looked at them.

"I....I don't think there is enough here..." Rita said. ".... I am really sorry but I don't think Sirena and Bella gathered enough..."

"Really?" Sirena asked, sounding as surprised as she could.

"We're really sorry," Bella said.

"It was just getting too dark," Sirena added.

"Is not your fault," Rita shook her head. "The potion will be fine in this state. Tomorrow, we can collect more coral and add it to the potion."

"What about Cleo?" Lewis asked. "How are we going to save her?"

"I'm afraid there isn't a whole lot we can do, yet," Rita shook her head.

"We may have to wait until Rikki is better before we go face Erik," Mimmi added.

Lewis sighed and put his head in his hands.

"We are really sorry," Zac put his hand on Lewis's shoulder. "But we will find Cleo, I promise."

Just then a buzz came from Evie's pocket. She pulled out her phone. "It's from Carly," she told them. "David says it's okay for us to stay at the café tonight."

"You should go there now," Rita said.

"What about Rikki?" Will asked.

"She should be fine here," Rita responded. "I'll close up the sea entrance to my house. She'll be safe."

"Can-" Nixie paused. "Can I stay with her?"

Nixie was allowed to stay with Rikki, and everyone else went to the café.

"Hey guys," David said when they entered. "Sirena!"

Sirena paused for a moment. "Hi David," she smiled, walking towards him.

"Are you okay?" David asked, taking Sirena's hands.

"Yes, I'm fine." Sirena paused. "Thank you."

David smiled. "I'm glad." He turned to face everyone else. "There's fish in the cool room, and plenty of drinks. Carly and Cameron will be coming soon too."

"We best get ready to sleep," Ondina asked.

"Sirena?" Evie asked.

Sirena had been staring at the window, looking out to sea. "Hmm?"

"Are you okay?" Everyone looked at her.

Bella slowly walked over to Sirena, and looked out of the window too.

"...They're not okay," Lyla sighed.

"What do you think happened when they went to get the blue coral?" Mimmi asked.

"Maybe they met Erik and Charlotte?" Will suggested, shrugging slightly.

Emma snapped her fingers. "It was the Siren Song. I remember Mrs Chatham's warning: she told Bella to becareful of a song. And she told Cleo about being aware of an enemy, Charlotte. And she told Rikki to be careful of a drink!"

"Oh wow, you couldn't have told us this sooner?" Ondina questioned Emma, very angrily.

"I completely forgot about it until now," Emma replied.

"So even though Sirena and Bella didn't finish singing the song they may still have been affected?" Mimmi asked.

"What!?" David half yelled. "Sirena's a siren?"

"We will get it sorted," Evie promised.

"We just need to make sure they don't get left on their own," Zac nodded.

Just then Cameron and Carly walked into the café.

"Whoa, there are a lot of Fish Chicks in here!!!" Cameron yelled.

Everyone quickly exchanged hugs and handshakes, and then Carly and Cameron were told what had been going on.

They managed to keep Bella and Sirena busy for a few hours by giving them lots of food to eat.

"How are we going to help them?" Carly asked, nodding towards Sirena and Bella.

Everyone turned to look at Mimmi.

"How am I suppose to know?" She asked.

"It was your who warned us about the song as soon as they started singing it," Evie reminded her.

Mimmi closed get eyes and thought hard. "Well, Erik if controlling them, so I think only he will have the power to remove the curse."

"Isn't there another song they could sing?" Ondina asked. "Like, a song that could remove the Siren Curse? Reverse The Siren, or something!?"

"I honestly don't know," Mimmi sighed, opening her eyes. "But maybe Rita could make a potion that will numb Erik's connection to them? So they can tell us if they know what Erik is planning?"

Zac nodded. "We best get some sleep. I'll take the first watch, and I'll swap with Will in an hour or so. We'll need our strength, we have a busy day tomorrow. Goodnight, everyone."