“Well, technically, three days. You’ll leave on Friday.”

  “Friday,” I said, just to confirm I’d heard right. Three days to get our parents to agree to let us go off on a dangerous mission that we couldn’t even tell them about. “And we’re going to the Land of the Midnight Sun,” I added. “Which is?”

  “Which is in the very far north of the planet,” Neptune said. “A place where, for many weeks in the summer, the sun does not set.”

  “At all?” Aaron asked.

  “At all. It is constant daylight. Now, listen. I have told you about a mountain, and about a lake. They are linked. The lake is surrounded by the mountains. You must find this place. When you gaze into the lake, you will not be able to see the bottom — all you will see is the reflection of the mountains around it. But here is the thing — the reflection will not match the reality.”

  “Huh?” I said.

  “I can’t explain it better than that,” Neptune said. “All I know is that what you will see around you is not exactly what you will see in the lake. You must find this lake. One of the mountains surrounding it is covered in a glacier that looks like a giant’s tongue spreading down the mountain. This is where you will find my answers.”

  I let out a breath. So basically we needed to find a place where what we saw wasn’t really there, and then climb up a tongue into a giant’s mouth. Excellent.

  Neptune swam across the room and beckoned for us to follow. Batting away a brown-and-cream striped fish that looked as if it were dressed in pajamas, he reached into a drawer with handles like cobras and took out two shells. “Take these,” he said, passing us one each.

  I turned the shell over in my hands. It was shiny purple, with a spiral winding tightly around the top, opening up into a fatter shape in the middle, with a big gap that went into the center of the shell. The kind of shell you’d hold to your ear so you could hear the ocean. Aaron’s was silver. Neptune held a third one; it was gold.

  “You will use these to communicate with me. They are not ordinary shells. They are shell phones. They are infused with my magic, and with them you can contact me — no matter where you are, no matter what time of day or night.”

  “How do we use them?” I asked, turning my shell over in my hands.

  “You say out loud the color of the phone you want to speak to — purple, silver, or gold — and that person’s shell phone will light up. When they pick it up, speak into your shell. They will hear you. Are we clear?”

  We nodded.

  “I need you to keep me up-to-date with any important information.”

  I opened my mouth to ask a question. He answered it before I had the chance.

  “If you don’t know whether something is important or not, assume it is and contact me. Understand?”

  “We understand,” we said together.

  “Good. Now — take these as well.” He reached back into the drawer and pulled out two small bottles. He handed us one each.

  “What are these?” I asked, studying my bottle. It looked like the kind of thing Millie kept her herbs and potions in — a tiny glass bottle with a cork in the top and a bright-orange liquid inside that shimmered and glowed like smoke from a flare.

  “The sea where you are going is far, far colder than anything you have swum in before,” Neptune said. “Full merfolk can adapt to all waters, but you are semi-mers and do not have that power. The first time you enter the water, you must put this on your scales. It will protect you. Use the whole bottle and it will let you swim in these waters for a week. That should be plenty of time.”

  Should be? What if it wasn’t? What if the mission took longer than that? I didn’t ask out loud. If Neptune thought a week was long enough for this mission, I didn’t want to argue for us to take longer.

  “Next,” Neptune said briskly, “I will arrange a cover for you.”

  “A cover?” I asked.

  “No one is to know where you are going, or why.”

  I considered pointing out that seeing as, strictly speaking, we didn’t actually know where we were going, he was pretty safe on this one.

  “Mr. Beeston will escort you,” Neptune went on. “He will be told that this is a special secret task for me — but he will not be told about the nightmares, or the extent of the threat.”

  “Why Mr. Beeston?” I asked. “Why not our parents?”

  “Beeston can live on land and in the sea,” Neptune explained. “Both may be needed. And for all his faults, he can be trusted.”

  I swallowed any reply to that.

  “I will arrange all the details and send Beeston to see you when it is done,” Neptune continued. “Are we clear?”

  Were we clear? I held back a nervous laugh.

  “Listen,” Neptune said. “This is all you need to know: there is a threat; it is big; it will come from the Land of the Midnight Sun; you are to stop it and find out who stole my memory. It’s as simple as that.”

  The nervous laugh I was holding back froze in my stomach as the extent of our task really began to sink in.

  “I will always be grateful to you,” he added. “When this is over, there will be rewards.”

  “We understand,” Aaron said.

  Finally finding my voice, I added, “We’ll do everything we can. We won’t let you down.”

  Neptune looked at us both and smiled. “I know you won’t,” he said. “That is why I chose you.”

  Neptune was true to his word in getting things organized.

  The next morning, Aaron was over at my place. Aaron’s mom and Millie were around, too. Millie was reading Mom’s tarot while Aaron and I looked on and tried not to burst out laughing every time she said things like “The empress next to the four of cups — very auspicious,” in a deep, meaningful voice.

  Dad turned up halfway through the reading, poking his face through the trapdoor in the floor and leaning his arms over the side as he blew a kiss to Mom.

  “Shhhhh!” Millie hissed. “I’m fully attuned and I don’t want you disturbing the spiritual essence of the tarot.”

  Which made me want to laugh even more.

  Just as Millie was finishing the reading and had begun to shuffle her cards, there was a sharp rap on the door.

  “Only me,” Mr. Beeston called as he stepped onto the boat and looked around. “Ah, good. I’m glad you’re all here. I have some important news.”

  “Sounds ominous,” Millie said.

  “Not at all,” Mr. Beeston said. “In fact, it’s very exciting news.” He turned to Aaron and me, then looked back at the others and smiled his wonky smile. “It concerns Emily and Aaron.”

  “Uh-oh,” Dad said with a wink. “What have they been up to now?”

  Mr. Beeston gave Dad one of his I’m-very-important-and-I-know-a-lot-more-than-you looks. “What they have ‘been up to’ is impressing Neptune so much with all their recent actions that he has decided to reward them,” he said.

  “What kind of reward?” asked Mom.

  Mr. Beeston cleared his throat. “He’s sending them on a vacation.”

  “A vacation? Oh, how wonderful!” Mom said, almost bouncing in her seat. “Where are we going? When are we off?” She jumped off the sofa. “Ooh, what do I need to pack?”

  “Ah, well, that’s the thing.” Mr. Beeston reddened.

  Mom stopped bouncing. “What’s the thing?”

  “You . . . er . . . well, you don’t need to pack anything, actually. At least, not for yourselves.”

  Mom stared at him for a moment, and then she brightened again. “You mean Neptune is providing us with everything we need?”

  “Neptune is not providing you with anything!” He fiddled with the bottom of his jacket as he added, “I’m afraid you won’t be going.”

  Mom and Dad exchanged a glance. “They’re going alone?” Dad asked.

  Mr. Beeston flushed even deeper. “No, not alone,” he said. “They will, of course, have a chaper one to escort them. Neptune has thought carefully about this imp
ortant decision, and he has come to the conclusion that he must send one of his most highly trusted, elite, superior —”

  “YOU?” Mom burst out. “He’s sending you?”

  “Er, yes,” Mr. Beeston said, suddenly noticing something very important to look at on the deck.

  “Why not us?” Dad asked.

  “He . . . er . . . well, I mean, apart from the fact that I have been a highly trusted member of his staff for many years, I suppose he —”

  “He wanted someone with a tail and legs,” Aaron cut in.

  “At least, that’s what we would guess,” I added quickly, glaring at Aaron. We weren’t supposed to know anything about this yet!

  “Yes, that’s what I meant,” Aaron blustered. “I mean, it makes sense, doesn’t it?”

  Mr. Beeston gave us one of his funny sideways looks. Did he know we already knew about this? That we knew more than he did?

  “The children are probably right,” he said. “Neptune would have wanted a semi-mer to go with them. And, of course, someone he trusted. Someone of a high rank. We leave on Friday.”

  Mom tried to look pleased for us, but failed. “You will look after them, won’t you?” she said eventually.

  “Of course I shall look after them,” Mr. Beeston said. “That is precisely my job.”

  Dad smiled at us. “Well, I think it’s great,” he said. “I’m proud of you both.”

  “Me too,” Aaron’s mom added, coming over to give Aaron a hug.

  It was only when Dad said, “Hey, kids, you could look a bit happier about it, you know,” that I realized we were supposed to be acting as though we really had just found out we were going on a wonderful, all-expenses-paid holiday.

  “We were just in shock,” Aaron said woodenly. “It’s great news, isn’t it, Em?”

  “It’s fantastic,” I said, pinning a smile on my face. “Yay,” I added for good measure, trying very hard not to let anyone see how much I was shaking.

  Just then, there was a noise from the lower deck. Dad looked down. “It’s Archie,” he said. “Come on up,” he called to Archie. “You’re just in time to hear the news.”

  Archie swam up and joined Dad, leaning on the trapdoor. Millie went over and bent down to kiss him.

  “What news is that?” Archie asked, smiling broadly at Millie. Honestly, those two were so loved up — they were worse than Mom and Dad!

  “We’re going on a vacation!” Aaron said, making a bit more effort to sound as though he believed it were true and didn’t actually know that we were being sent to a place so scary and so dangerous that Neptune himself didn’t want to go there.

  “That’s wonderful,” Archie said, still smiling. “All of us?”

  “No — just Emily and Aaron,” Millie trilled. “It’s Neptune’s treat!”

  Archie’s smile faded instantly, like a dark cloud coming out of nowhere to cover the sun and make everything cold. “Neptune’s what? Neptune’s sending them away? Where are they going?”

  Mr. Beeston took a step forward and cleared his throat in his I-know-you-work-for-Neptune-but-I’m-clearly-the-most-important-person-here kind of way. “It is by way of a thank-you, a reward, as it were,” he said. “Emily and Aaron have done some great things lately, and this is Neptune’s way of showing his gratitude.”

  Archie nodded slowly. “I understand,” he said. “In that case, I have to go to see Neptune now. They will need escorting. I must insist I go with them.”

  “Oh, darling, you’re so lovely,” Millie said gently stroking his cheek. “You’d do anything to help Neptune, wouldn’t you?”

  “Of course I would,” Archie said.

  “Ah, well, actually, it’s all sorted out,” Mr. Beeston said. “I have already been asked to escort them. So, on this occasion, you won’t be needed.”

  Archie’s face paled. He stared at Mr. Beeston, no doubt angry at being shown up in front of us all. “I have to go,” he said eventually. “I’ll see you later.” And with that, he flicked his tail, dived back down to the lower deck, and swam away.

  “Huh!” Millie said. “He didn’t even kiss me good-bye!”

  “Well, at least he seemed pleased for us,” I said sarcastically. I mean, what exactly was his problem?

  “He’s probably just jealous that he wasn’t Neptune’s first choice as chaperone,” Mr. Beeston said, a little smugly.

  “Hey, did he mention that we popped over to see you on Monday, by the way, about five o’clock?” I asked Millie.

  “No. Are you sure?” Millie asked.

  “Positive,” Aaron replied. “Archie was there. He said he’d come over to take you out on a surprise date.”

  Millie smiled indulgently. “How sweet, but you must have the wrong day. Archie knows full well that I have my Aura Reading class then. I wouldn’t cancel it for anything — not even a date with him!”

  We hadn’t gotten the wrong day, but I didn’t say anything. If Millie wanted to believe Archie was the most romantic being on the planet, let her. I wasn’t quite so sure what he was. Right now, he seemed to be turning into someone who just acted strangely. Or maybe I was letting everything get to me too much.

  I suddenly felt the need to escape. “I’m going out,” I said.

  “But you can’t; you’ve got to pack for your vacation!” Mom exclaimed.

  “Are you all right?” Dad asked.

  “Shall I come with you?” Aaron added.

  “I’m fine. I can pack later. I just need to be on my own for a bit,” I said. I didn’t want to be with any of them right now.

  It was only once I’d left the boat that I knew exactly where I needed to go, and who I needed to see. And I couldn’t get there fast enough.

  “Emily!” Shona opened her front door and swam out to meet me. She took hold of my arm. “Come on in; Mom and I are making crab cakes.”

  “Can you come out instead?” I asked.

  “What’s wrong? Are you OK?”

  “I just want to hang out on our own.”

  Shona smiled. “Swishy — it’s been ages! I’ll tell Mom I’m going out.” She disappeared inside.

  I felt guilty at that. I knew she meant that I was always with Aaron nowadays.

  “Mom says I have to be back in an hour,” Shona said, swimming back and shutting their big porthole door behind her. “Where do you want to go?”

  “Rainbow Rocks?” That was where I’d first met Shona, and who knew — maybe this would be the last time I’d ever see her, if it all went wrong.

  We swam to the biggest of the rocks and pulled ourselves to the water’s edge. Shona perched on the edge of the rock, her tail flapping in the water. I lay on my tummy at the sea’s edge, flicking my tail in the waves behind me.

  “Shona, I’ve got something important to tell you,” I said.

  Shona’s tail stopped flapping. “What is it?” she asked. “Is it you and Aaron? Have you broken up?”

  “What? No! Of course we haven’t!”

  “Oh, good,” Shona said, although I’m sure I saw a tiny flicker of disappointment in her eyes. “What, then?”

  “I . . . I’ve got to go away,” I began.

  “Away where? For how long? When?” Shona fired questions at me.

  “I don’t know for how long,” I said. “I’m leaving the day after tomorrow.”

  “How come you haven’t told me this till now?” She looked hurt. Then her face seemed to close up. “Are you going with Aaron?”

  How was I supposed to explain? I wasn’t allowed to tell anyone anything, but I really wanted to give her something. I didn’t want her to think I was just going off with Aaron on a big adventure that she was excluded from.

  Then I realized what I could give her. I reached into my tail pocket and pulled out something that I always carried with me: my friendship pebble. Shona and I had given each other these ages ago as a symbol of our friendship — and of the fact that we would always be there for each other, no matter what.

  “I want you to have this,
” I said.

  “But it’s yours!” Shona said. “If I take it, what will you have?” Then her eyes danced with an idea. She reached into her own tail pocket and pulled out her identical pebble. “Let’s swap them! That way, we both have something really special of each other’s.”

  “Kind of like saying we’re not really apart?”

  “Exactly!”

  We swapped pebbles, and Shona looked a bit happier. But it still wasn’t enough. I wanted to give her more. Then I had a thought. I had my shell from Neptune on me. What if I gave it to Shona? We’d still have Aaron’s, so we could talk to Neptune, but it would mean I could keep in touch with Shona while we were away, too. And it would really show her how important she was to me.

  Before I could talk myself out of it, I pulled the shell out of my pocket. “Shona, take this,” I said.

  She looked at the shell. “What is it?”

  I took a breath. How much could I tell her? “Neptune has organized this trip,” I said. “He’s told everyone it’s a vacation, but . . .” I stopped. “Look, promise you won’t tell anyone.”

  “Of course I won’t. I thought you knew you could trust me.”

  “I do. That’s why I’m telling you.” I glanced around nervously and lowered my voice. “It’s not a vacation,” I whispered.

  Shona leaned in and whispered back, “What is it?”

  “A mission.”

  Shona’s eyes widened. “A mission? That sounds exciting!”

  I thought of Neptune’s nightmares, his fears. “Hmm,” I said. “Maybe. But listen — he’s given us these shell phones. We can talk to each other with them. I want you to have mine.” I held out the shell for her. “We’ve still got Aaron’s to talk to Neptune, and you can call me on that one. Just say ‘silver’ into the shell, and Aaron’s phone will light up.”

  Shona took the shell phone and turned it around in her hands. “Really? You’re sure?”

  I nodded. “For emergencies only, OK?”

  Shona closed her hand around the shell. “Like if I’m missing you too much, or have some gossip that I absolutely have to share with you,” she said, smiling.

  I smiled back. “Exactly!”

  Shona laughed softly. “No, I know it’s not for that. I probably won’t use it. I don’t want to get you into trouble. But I’m glad you gave it to me.”