"That's what I thought you'd help me work out."

Shona grabbed my hands. "I will, Emily," she promised. "We'll stop this from happening, OK? As sure as sharks have teeth, I'm not going to lose you. Whatever happens. And you're not going to lose your parents either."

I winced at her words as though she'd lashed me with a piece of wire. Just the thought of it!

"We're going to solve this, all right? You and me, we can do anything, can't we?" Shona looked at me desperately, her eyes begging me to say yes.

I looked at her and squeezed her hands. "Of course we'll solve it," I said, lying as much as she was lying to me with her words, and as much as Millie had lied with her smile. "Of course we will."

I stood on the front deck with Millie. Shona was in the water next to the boat. I rubbed my stomach, trying to ignore the fact that it was rumbling from my rationed dinner of a third of a can of beans and a piece of toast. A feeling of warmth spread into me from the ring, against my body. Everything was going to be OK. I could feel it. The ring was telling me so.

"That's the Plow, and that's Orion's Belt," Millie said, pointing up at the stars, cl.u.s.tered together in tight clumps. I craned my neck to follow the outline she was pointing out. I don't know how she could tell what was what. The longer I stared, the more it just looked like a completely black sky filled with a million billion tiny white dots.

"What's that?" I asked, pointing to a dark shape like a shadow in the distance. It was coming closer, changing as it slid across the sky. Another cyclone? Please, no!

It looked like a giant snake, gathering and bunching up into an arc, then stretching out to form a long black line cutting through the stars. It was heading for the castle. The shape disappeared into the mist, reemerging above it to swirl around the top of the castle, circling it, spinning into a spiral, around and around, tighter and tighter, faster and faster, until it faded into nothing. It was one of the strangest things I'd ever seen. And one of the most magical too.

We stared into the black night. The shape didn't come back.

"I have no idea," Millie said eventually. "I've never seen anything like it in my life. And I'm not one for superst.i.tion, as you know, but I'll bet it's portentous. Let me think."

"What about the stars, though?" Shona asked. "There are constellations that can help us work out where we are, I'm sure of it. I just can't remember what they're called. Or what they look like."

Which was a big help.

"I've got it!" Millie said, her eyes brightening. "I have a great idea." She headed back inside the boat and beckoned me to follow.

For a moment, for one silly, ridiculous, heart-stopping moment, I actually thought she'd come up with a plan to get us out of this. I let myself hope. Until she said, "I'll do our tarot cards."

I followed Millie into the kitchen. "You clear a spot for us, and I'll lay out the cards," she said.

Shona swam up to the trapdoor as I pushed a couple of chairs to the side. She poked her head through, and I sat on the floor by the trapdoor to join her. Then Millie came in with the cards and we watched intently as she shuffled, spread the cards in a six-pointed star, and slowly turned them over one by one. She didn't speak, didn't explain anything. When they were all faceup, she sat looking at them for ages, nodding slowly.

"What do they say?" Shona asked.

"Do they say anything about my mom and dad?" I asked.

"Or mine?" Shona added quietly. That was the first time I had really thought about her parents. She'd been taken away from them too. They wouldn't have a clue what had happened to her. They hadn't seen her since she went to school that morning. I'd been so selfishly wrapped up in my own problems, I hadn't thought about Shona's.

Would anyone tell them anything back at Allpoints Island? What would happen when Mom and Dad came home a" a.s.suming they ever did a" and found that Fortuna wasn't even there? Would they come after us? Would they know where to look? They'd find out, wouldn't they? But what if they didn't? Suppose they didn't come home at all! Suppose they'd had such a big fight, they'd split up and both forgotten all about me!

No! I couldn't let myself think like that. I couldn't! Surely they'd do something. They'd get together with Shona's parents and send out a search party or something.

They'll find us. They'll find us. They'll find us. I repeated the phrase over and over and over like a mantra. Please let me believe it, I added.

The cards didn't tell us anything. Anything beyond what they normally said when Millie read anyone's tarot cards. We had a long journey ahead and the outcome was uncertain. A tall, skinny stranger with jet-black hair would help guide us, the truth would elude us, and all would be well in the end. Blah, blah. Why I ever put faith in Millie's card reading, I don't know. It was about as useful as trying to tell the time from examining your freckles.

"Look, let's all try and get some sleep," she said, shuffling the cards away when it was clear they hadn't impressed either of us or helped us find an answer to any of the questions we weren't saying out loud. "Things are bound to look better in the morning, once we've had a few hours' nap a" and perhaps a cup or two of Earl Grey."

I stifled a laugh. Admittedly, a slightly hysterical one. It was really pretty hard to see how things were going to look better. But she had a point about the sleep thing. I was exhausted.

"Shona, you take Jake's room," Millie said. "You'll be all right down there, won't you?"

Shona bit her lip and nodded.

"I'll join you if you like," I said softly.

"No, it's OK. I'll be fine."

"I'll be just above you. Knock if you need me."

Shona smiled, although her eyes stayed misty and sad.

"It'll look better in the morning," I said, repeating Millie's lie. It kind of helped to keep saying these things out loud. If we did it often enough, perhaps they'd come true.

"Night-night, you two," Millie said. "I'm going to get some shut-eye myself now. Although G.o.ddess only knows how I'll sleep without my agnus castus tablets."

We each withdrew to our own rooms, our own thoughts, and our own fears.

The moon rose as I lay on my bed. I watched it climb past the porthole. A fat, wonky shape like a slightly deflated ball, it shone down on me, right at me, as though it were personal. Just me and the moon, staring each other down. It was getting fuller every day, every single moment. Racing me to my fate.

The black sky, endless behind it, filled slowly with clouds: some huge and unmoving, like snow-clad hills, others gray and broken-up, like crazy paving. Lighter, wispy clouds sailed slowly in front of them all. And the moon stood firm, almost whole, like a circle drawn freehand by a child. Not quite perfect but not far off.

"Please let this be a dream," I whispered, twisting the ring around and around on my finger, talking to it as though it could hear my thoughts and turn them into reality. Was it a friend or enemy? What was its hold over Neptune a" and over me? I couldn't tell. All I had was the knowledge that it was caught up in this whole nightmare with us a" and the tiny feeling that it might help us find our way out of it too.

Please let me be back at Allpoints Island in the morning, I prayed. Please let me hear Mom and Dad arguing in the kitchen as soon as I wake up. Please.

Next time I looked, the clouds had all moved on. The stars were no longer visible either. Just the moon remained, bright and proud. See? it seemed to snicker at me. I win.

There was a split second as I woke up when everything felt normal. Any second now, Mom would call me to get up and I'd have to drag myself out of bed. She hadn't called yet, though. Still half asleep, I stretched and turned over in my warm bed. I was about to go back to my dreams a" and then I remembered.

I sat bolt upright, then jumped out of bed and ran to the porthole. Let me see Allpoints Island. Let us be back there.

I was greeted by the sight of mauve sea stretching out forever, everywhere I looked. Baby-blue sky. And the white line of mist hovering in the middle, dividing the two worlds.

"Emily, are you up?" Shona's voice called quietly from below.

I ran to the trapdoor and dropped myself down to join her. As soon as my legs touched the water, I felt them change. Please work properly this time, I said to myself, and I held my breath as I felt my tail form. Closing my eyes, I focused for a moment on the feeling, willing it to work completely. But it didn't. In fact, it was worse than before. Patches of scales were missing; the shine of my sparkling tail seemed duller; my tail moved more stiffly.

I swallowed my feelings and hoped Shona wouldn't notice. I still didn't want to admit it out loud: I wasn't a mermaid half the time anymore. Now I wasn't even close to being a real mermaid.

"Look." Shona pulled me over to the large porthole door. We swam out through it, around the huge sandbank under the boat, and up to the surface, where we rested, treading water by the side of the boat. Directly ahead of us, hovering on the line of mist as though it were floating, the castle stood bold and gleaming in the sunlight. "I think we should go to it," Shona said, echoing my thoughts from yesterday.

"On the boat? How? You saw the sails."

Shona was shaking her head. "No, I meant just you and me. We could swim there. It doesn't look far."

It was still early. I could tell by how low the sun was in the sky. In fact, now that I looked, I could still see the moon, hanging on like the last guest at a party, reluctant to leave but fading and tired. Could I edge ahead in the battle that was silently taking place between us? Millie would still be in bed. She always slept late. We could get there. As soon as the thought came into my mind, my hand grew hot. The ring a" it was telling me something, I was sure of it!

It was telling us to go.

"Come on," I said, feeling hopeful for the first time since we'd landed here. "Let's do it."

"How long have we been swimming?" I asked, panting to catch up with Shona. Surely she was swimming faster than usual! I could hardly keep up with her.

"Not sure. Maybe twenty minutes, half an hour, tops."

I stopped where we were and flicked my tail around in fast circles to tread water. "Look," I said, pointing to the castle. It seemed to be looking back at me, willing me to approach it. Pulling me along. But there was a problem. A big problem.

Shona looked across at the castle. "What?"

"It's no closer. It looks just as far away as it did from the boat."

"Don't be ridiculous," Shona said with a laugh. "It's just . . ." Then she glanced back to see where we'd come from. Fortuna was a dot in the distance. She turned back toward the castle. "But that's . . . but it's not possible."

"It's like a rainbow," I said. "The nearer you get to it, the farther away it seems."

"But how?" Shona's voice broke into a whine. Her eyes moistened as her bottom lip began to tremble. I almost expected her to howl, "I want my mommy!" And why shouldn't she? That was certainly what I wanted to do. I felt like a burst balloon.

"Come on," I said flatly. "Let's go back to the boat. Maybe Millie will have some idea what's going on. You know she thinks more clearly in the morning once she's had a cup of tea."

"Or ten," Shona added with a hint of a smile.

I smiled back. "We'll figure it out," I said. "Don't worry."

As we swam back, I didn't tell her how stiff my tail was getting, how it was starting to feel as if I were dragging a lead weight behind me. Or how that was part of the reason I felt defeated. I pretended I wanted to go more slowly to take in the view: the sea, calm and smooth as we cut through it, the mist lying low and still on its surface.

Eventually we got back to the boat and swam in through the porthole. Almost as soon as we did, Millie's voice warbled down to us. "Emily? Shona? Is that you?" she called, an edge of panic in her voice.

"Hi! We're here!" I called back.

"Oh, thank heavens," Millie breathed, her face appearing at the trapdoor as she leaned over it to look down at us. "Where have you been?"

"We just went out for a quick swim," I said.

"Emily." Millie's tone had turned serious. Her voice a low rumble, she said sternly, "You must never, ever, go out without telling me again. I am responsible for you. I would never forgive myself if anything happened to you. Do you hear me?"

"I'm sorry," I said. "We were just a""

"It doesn't matter now." Millie waved the rest of my sentence away. Just then, I heard a cough from somewhere behind her.

"Who's that?" I blurted out. My heart lifted. Mom and Dad were here after all! They were waiting for the right moment and were going to appear any second, with big smiles, and tell me this had all been a joke, or a mistake, or a"

"There's someone to see you," Millie said in a voice as flat and lifeless as a dead eel. And then, cutting my hopes like the sharpest knife, a face appeared next to hers.

Mr. Beeston.

"h.e.l.lo, girls," he said, squinting down at me and Shona.

"What are you doing here?" I asked through a tight throat. "How did you find us? Where are my parents?"

"Now, now," Mr. Beeston said with a crooked half smile. How could he smile? Didn't he understand anything that was going on? Or was I mistaking him for someone who cared? "One thing at a time. You calm yourself down and then meet me on the front deck." He nodded at Shona. "And you too, child," he said. "You'll all need to hear what I have to say." He pulled back a sleeve of his old nylon suit to glance at his watch. "Let's say ten minutes." And then he was gone.

"I'll be with you," Millie said softly. "I'm not going to leave your side till we've got this settled, all right?"

I nodded. My throat felt too thick and too dry for me to speak.

Mr. Beeston was waiting on the front deck, sitting on a bench and looking around at the horizon.

"Now then," he said as Millie and I sat on the opposite bench. Shona perched on the edge of the deck, her tail draped loosely over the side, flicking the water with tiny splashes. How much longer will I be able to do that too? I glanced at my hands. The skin reached up along my fingers now, joining them together, lodging the ring even more tightly in place. What was happening to my body? It was just as Neptune had said. Until the curse was complete, I wouldn't be one thing or another. What did that make me? A nothing?

I couldn't bear to see the evidence, so I stuffed my hands in my jeans pockets and waited for Mr. Beeston to explain what was going on.

He cleared his throat. "Now then," he said again, "you are probably wondering why I'm here."

D'you THINK?

I bit my lip. It was never a good idea to interrupt Mr. Beeston. It only took another half hour for him to get going again. He wasn't a big fan of sarcasm either a" or of nerviness. Or of me. So I kept my mouth shut and counted to ten.

"As you know, I was entrusted by Neptune with a most important job. And, as you also know, there had been a certain amount of disturbance, which I was in the process of endeavoring to correct. In fact, even as I speak, some of the folk at Allpoints Island are gathering the final few items of lost treasure. The project has been very successful, largely thanks to your resourceful teacher. All of which helps make Neptune happy. However, as we all know . . ." At this point, he looked around at the three of us with one of his crooked smiles, trying to include us, as though we were all in this together. How could we be, when he was the only one who had any idea what was going on?

Again, I stopped myself from saying anything. I counted to twenty this time.

"As we all know," he repeated, "the situation has changed somewhat. Since events took the turn they did, Neptune's attention has wandered from his initial intentions. And so we have found ourselves in this situation."

He folded his hands in his lap.

"What situation?" Millie asked. "I don't have the slightest idea what you are talking about. Now, are you going to explain what in the cosmos is going on here, or am I going to have to a""

"Calm down, calm down." Mr. Beeston waved a hand at her. "I am getting to it."

Then he fixed his eyes on me. "Emily here has found something we never even realized was there, something that Neptune wants back, and perhaps if I tell you a little bit about it, you will understand why. Then maybe we can work together to solve the problem, and all will be well."

"*All will be well'?" I exploded. I couldn't stop myself this time. There weren't enough numbers to count to that would halt my rage. "All well? We're lost out in the middle of the ocean with nothing but sea and mist and a spooky castle that doesn't even seem to exist. Shona's parents haven't seen her since yesterday morning. My parents have been arguing and probably never want to see each other or me again a""

"Come on, Emily. You know that's not true," Millie interrupted me.

I ignored her. "And, to top it all off, Neptune's done this!" I pulled my hands out of my pockets and held them out in front of me. The skin had reached even farther up my fingers. They were joined at least a third of the way up, lodging the ring so tightly on my finger it hurt.

"Emily!" Shona gasped, edging forward to look more closely at my hands. "What's that?" She looked disgusted. I knew she would.

"I didn't want to tell you," I said. "I didn't know if you'd still want to be my friend if you knew."

"Knew what?"

"The curse. It's already started," I said. "I'm not a real mermaid anymore, or a real girl. I'm nothing."

I felt a couple of tears roll down my cheeks, salty drips running into my mouth.