Aaron's tail flashed as he flicked it sharply. He was getting impatient. "Where do we fit into all this?" he asked. "You said you'd tell us your story if we promised to help you. What do you want us to do?"

Morvena met his eyes with a firm stare. "All I know is, you can work some kind of magic. You can get out through the waterfall! No one has ever managed that before - not even the sea life that is down here with us. It gets in. But, like us, it doesn't get out."

"But it was only the two of us who could get out," I said. "Just me and Aaron. We couldn't get Shona through with us."

"I know. I saw that, too."

"Then I don't see how we can help."

"Listen. Here are the facts. You have powers. You can do things that none of us can do. Agreed?"

I looked at Aaron. "Agreed," he said.

"And from what I've observed in here, I am now convinced of one thing. Melody's sh.e.l.l is the key out of here. Whatever it is that Melody lost, whatever it is that she has begged the sh.e.l.l to help her find, I'm positive it is our only hope. Even though she has let us believe the way out of here was through singing, I'm sure this was always a diversion to keep the others calm, and to stop us from questioning her too much and finding out the truth that she's fought so hard to keep secret. Even I have never gotten close to knowing this secret. All I do know is that the only thing she has put any faith in to get us out of here is the sh.e.l.l."

"OK, I'll go along with that, too," I said. "But I still don't see how -"

"Wait," Morvena said. "Don't go anywhere." Then she swam to the opening and out through the seaweed curtain. She must have been gone for at least five minutes. When she came back, she was holding something.

She opened her hand out to reveal a glistening, beautiful, pearly sh.e.l.l. "She goes to it every morning and every night without fail, but never in between," she said. "She won't miss it now until this evening."

"You've stolen it from her!" Shona exclaimed. Her idea of what it is to be a best friend was taking a hammering.

"I've borrowed it, to help us all," Morvena insisted. "Melody will get it back before she knows it's gone. Whatever magic the sh.e.l.l holds, maybe your magic can bring it out - especially if you take it away from here. The sh.e.l.l will never get the chance to share its secret bound and trapped down here with us."

"What if you're wrong about all this?" I asked.

"If I'm wrong, as long as it's back in her room by tonight, we haven't lost anything. If I'm right and you can reveal the sh.e.l.l's secret, you could save us all." She looked at Shona, and then back at me. "Including your best friend," she added.

I turned to Aaron. "What do you think? Should we?"

Aaron shrugged. "Like Morvena says, what is there to lose?"

"OK," I said, reaching out to take the sh.e.l.l from Morvena. "We'll do it."

Aaron and I swam up the well. Looking down, I could see Shona and Morvena staring up at us. "Look after her!" I called down. "Don't let them hurt her!"

"I promise!" Morvena called back up to me. She reached out to pull Shona toward her and held a protective arm around her.

"I think we can trust her," Aaron said to me. "After everything she's told us today, she's got as much to lose as any of us."

"I guess so," I said, tightening my grip on his hand. Holding the sh.e.l.l carefully in my other hand, I gave a sharp flick with my tail.

Moments later, we were through the opening at the top and swimming away from the sirens, away from the caves, away from Shona - taking two things away with us: the sh.e.l.l, and the question I had no idea how to answer.

How would we ever make it release its magic and get Shona out of that place?

I didn't want to go home. I didn't really want to set foot in Brightport at all. I'd almost forgotten about the newspaper and everything that had happened before I found the sirens' caves. It seemed like years ago! But now that we were in town again, it came flooding back.

"I don't want to see anyone," I said as we crept out of the sea onto the beach and shook our clothes dry.

"Just stop by your house and let your mom know you're safe," Aaron said. "Then come back to my house. We'll do it there."

I agreed reluctantly and headed home. It wasn't that I didn't want to see Mom. I just didn't want to go up to the pier and along the jetty and all the places between here and home where I could run into someone trying to catch a mermaid who might recognize my face from their newspaper.

"Hurry," Aaron called. "We haven't got long."

Aaron was right. I had to get home as quickly as possible - preferably avoiding any eye contact with anyone along the way - tell Mom everything was fine, put on a big false smile, and hotfoot it back to Aaron's.

"I'll be there in five minutes," I called over my shoulder. And then I ran home.

Mom was sitting on the front deck with Millie and Aaron's mom. I could see them from the end of the jetty. I was glad to see Aaron's mom here. At least that meant their cottage would be empty.

"Hi!" I said, all smiles. Mom looked up at me and smiled back so innocently that I could almost believe that the whole morning had been a figment of my imagination.

"Emily darling!" she said, waving me over. "I thought you were going to be at Shona's all day."

"Did you?" I asked nervously. "Why did you think that?"

"Mandy came over and pa.s.sed on your message. It's nice that you're friends again, isn't it?"

"Oh, yes, of course." I'd forgotten about asking Mandy to cover for me. Had that only been this morning? It felt like a lifetime ago.

"Come and sit down, sweet pea," she said.

Millie drained her cup. "Just pop in and put the kettle on first," she said. "I could kill for another cup of Earl Grey."

I went inside and turned the stove on in a daze. While I was waiting for it to boil, I grabbed some bread and made a sandwich. The morning's swim had been exhausting and I realized I was starving! How could they be sitting here so calm and casual when people were hunting down mermaids for cash prizes? Or while Shona was trapped in an underground cave with the meanest sirens in the world? It all felt unreal.

"I just wanted to let you know I'm over at Aaron's if you need me," I said when I came back out.

"Oh, chicken, aren't you going to join us for some lunch?" Mom asked, squinting up at me.

"I just had some. See you later, OK?" I tried to sound as though everything was normal. I wasn't going to start getting into it all with Mom - not after everything else that had been going on with her parents. I turned away before I could see any disappointment in her eyes.

I sauntered casually down the jetty, my cheekbones aching from the false smile and my limbs feeling like a marionette's, all loose and floppy as I tried to imitate the way I might walk on any other normal Sunday afternoon when I was off with my friends.

"Be careful!" Mom called to my back. In reply, I turned and gave her a quick wave. A moment later, I was on the pier and out of sight. I dropped the smile, broke into a run, and hurried over to Aaron's.

"I don't get it. It's just a sh.e.l.l," Aaron said. He was holding it in his hands, turning it around and around for the hundredth time. "It doesn't do anything!"

He shook the sh.e.l.l. He lifted it to his ear. "I mean, it does that thing that all conches like this do. It sounds like waves when you listen to it." He put the sh.e.l.l down on the table in front of us. "But that's it. Nothing else. I think Morvena's wrong. I don't think it's got anything magical about it at all."

I stared at the sh.e.l.l. "Why would Melody talk to it, though? Why would she hold it and cry over it every morning? We must be missing something."

"OK, maybe we are - but I've got no idea how we're going to figure out what it is."

I reached out to pick up the sh.e.l.l - and so did Aaron. As our hands touched, I got that tingly feeling in my fingers. I s.n.a.t.c.hed my hand away, embarra.s.sed in case he could tell how it made me feel when he touched my hand, in case it wasn't the same for him.

"That's it!" he said. "Of course! How could we be so stupid?"

"What is it?"

Aaron lowered his eyes and shuffled awkwardly. "Look, you know when I - when we - you know, kind of touch hands . . ." His voice trailed away.

"Uh-huh," I said, trying to keep my voice casual. Touch hands? Did we? Oh - maybe, yeah. I hadn't really noticed.

"Well, d'you ever get, like, a kind of tingly feeling?"

"You get it too?" I asked.

Aaron grinned. "Course I do!"

I smiled back at him. That meant he felt the same way I did. Maybe he was my boyfriend!

"Just - well, you know there's all the stuff about the power that we have," he went on. "You know, the thing about Neptune."

Oh. OK, so maybe it wasn't about him being so crazy about me that his skin danced in happy leaps because I was close. It was just about overturning a curse.

"Mm, yeah, that's what I was thinking too," I lied.

Aaron laughed. "As well as anything else," he said. He'd gone and read my mind again. And this time, his face had turned as pink as mine felt. He did feel the same way! I couldn't suppress a happy smile.

"Just now, when we touched hands, and we were both touching the sh.e.l.l too, did you feel it then?"

I considered lying. If I said I'd felt it, what if he laughed in my face and said that he hadn't? It could be a trick to get me to confess to my feelings for him so he could tell me he didn't feel the same way.

Then I thought about it a bit more. This was Aaron I was talking about. He wasn't like that. He would never do something like that.

"Yes," I confessed. "Actually, I felt it really strongly."

"Me too," he said. Then he lifted the sh.e.l.l and held it between us. "Link my fingers," he said. "If we hold hands and hold the sh.e.l.l between us, maybe something will happen. Perhaps the sh.e.l.l's magic has something to do with Neptune - and if so, maybe we can undo it!"

I took his hand. As soon as we touched, I felt the tingle again. First in my fingertips, then it traveled up my arm. Soon it felt as though it was spreading through my whole body.

"Look!" Aaron said. The sh.e.l.l had started to vibrate in our hands. I tightened my grip on his fingers so we didn't drop it.

"It's working - it's doing something!"

The sh.e.l.l rumbled and shook, and it was making a noise - a bit like the sound it had made when we held it to our ears, only about fifty times as loud! It was shaking more and more violently. And then, without any warning, it suddenly stopped.

We stared at the sh.e.l.l, at our hands, at each other.

It hadn't worked. Nothing had changed. So much for our magical powers.

"Now what?" I asked.

Aaron disentangled his fingers from mine and held the sh.e.l.l to his ear. "There's something inside it," he said, shaking it softly.

Then he pa.s.sed it to me. I turned it over and shook it. He was right! Something was jiggling around inside the sh.e.l.l! I shook it again. This time the thing inside dislodged itself a little so that I could see the tip of it inside the gaping spiral.

I reached in and tried to grab it. My fingertips touched the corner, but I couldn't grasp it. "It looks like a piece of plastic!" I said, dismay hitting me like a hard slap. We'd gotten it all wrong. Morvena was mistaken; there was nothing magical about the sh.e.l.l. We'd done all this for a piece of plastic that had probably been swept out to sea with someone's trash and ended up in the sh.e.l.l! We'd done it all for nothing.

"I can't get a hold of it," I said flatly.

"Hang on a sec." Aaron got up and left the room. A minute later, he was back, with a pair of tweezers. He held them out to me. "Now try."

Reaching carefully in with the tweezers, I gripped the corner of the plastic and pulled at it.

Soon, I'd pulled enough of it out to grip it with my fingers - but they were shaking. What if I was wrong and it was magical after all? What might we be about to find? I'd had enough surprises in the last few months to know that you don't always find the answers you're looking for without finding about fifty unwanted ones first.

I pulled it out and held it in my palm. I was right about one thing. It was just an ordinary piece of plastic. It looked like the kind of thing Mom used to wrap my sandwiches in for school. And it had something inside it - but it wasn't a sandwich! It looked like a sheet of paper, folded over and over into a tiny package.

"You do it," I said to Aaron, suddenly losing my nerve.

He took the bag and opened it up. "Time to find out what this is all about."

The knock at the door startled us so much, we both literally jumped out of our chairs, banging knees as we did so.

Aaron quickly shoved the sh.e.l.l and package on to another chair and slid it under the table. "Who's that?" he called.

"King Kong," replied a familiar voice. "Who do you think?"

Aaron opened the door. Mandy stood on the doorstep, peering into the cottage. "Thought I saw you," she said. "What's going on?"

"We - we're just -"

"Let her in, Aaron," I said, getting up. Aaron held the door open for her and Mandy came in. Sticking his head out and glancing quickly in both directions, he closed it again and followed her inside. The three of us stood in an awkward circle.

"Thanks for telling Mom I was going to be out for the day," I said.

Mandy shrugged. "No problem. How did it go, anyway - whatever you were doing?"

I didn't know how to reply. Where could I start? And I still couldn't stop a bit of me from wondering if Mandy really was being genuine - or if, any moment now, she would laugh in my face and tell me she'd just been pretending and had never had the slightest intention of being my friend.

"It's OK, I get it. You don't trust me," Mandy said, before I'd worked out how to answer her question.

"No, I -" I began. Then I stopped. I took a breath and started again. "It's not that I don't trust you," I said carefully. "It's - well, maybe I'm scared."

"Scared? Of me?" Mandy laughed. Then she flushed deep red. "I suppose I've given you reason to feel scared of me in the past," she said sadly. "I was a bully. I made your life terrible. I'm not surprised that's how you feel." She turned and headed back toward the front door. "Sorry for bothering you."

I grabbed her arm. "No! That's not what I meant," I said. "Don't go."

"Why not? Why on earth would you want to be around me? I was an idiot to think you'd want us to be friends," she said.

And despite everything that had happened today, and how much of a mess everything was, I suddenly got this really good feeling. It was like looking out at a calm sea and feeling at peace. Mandy and I were friends, and I had to stop doubting it. The only block to our friendship was me, and my silly suspicious mind. We had enough battles to fight without trying to turn our friendship into another one.

I patted the chair next to me. "Look, come and sit down," I said. "I'm going to tell you everything."