They'd seen no sign of the genie all day, which seemed a little strange when Giulia thought about it. It was easy enough to believe that it had moved on by now, but what about earlier? Signora Aragosta and her daughter had been in the ravine when they'd gone out to see Signor Donzella, and gone when they returned. The same with the Branzinos' son. In either case they could only have missed what happened by a few minutes.

Had they just been really lucky, or was there some other reason? The genie had said that neither Giulia nor the two 'sons of Oannes' would come to any harm. Had it deliberately left them alone because of that promise? That wasn't something Giulia really wanted to trust right now, and so she kept looking over her shoulder as they swam back to shore. It shouldn't have been possible for the ocean to seem eerily silent, with fish and crabs still moving around and seaweed rustling in the current, but it did.

Alberto didn't seem at all worried, but then, he refused to ever act worried, even when he was scared to death. Luca had no such fears for his image, and didn't bother pretending that he was anything but very frightened indeed. He kept close to his friends, occasionally taking their arms or hands to reassure him they were still there, that the genie hadn't snatched them away from him. If anything were to happen to Alberto and Giulia because they'd decided to go looking for Luca... well, Massimo and Helena might forgive him, but Luca would never forgive himself.

It was a big relief to hear the sound of a familiar boat motor. Giulia heard it, too, and she and Luca both looked to Alberto to see if it were who they hoped – he nodded and headed up.

"Massimo!" he called out, scrambling into the boat. "We're here!"

Massimo had been scanning the water for any sign of life, but he'd been facing the opposite direction. Hearing Alberto's voice, he cried out a phrase he would not normally have used in front of children, and turned around to make sure the boy was all right.

"Are Luca and Giulia with you?" he asked.

"We're here!" Giulia called out from in the water, at the same time as Alberto nodded eagerly. "Papà, we're right here!"

"Meno male!" exclaimed Massimo, and made the sign of the cross. He pulled Giulia into the boat while Alberto did the same for Luca, then wrapped a blanket around the three children. "Did you find anyone else?" he asked.

Luca shook his head sadly. "Just Signor Donzella. Everybody else was gone."

"Then we'll go back at once," Massimo decided.

He said nothing more as the boat bounced over the waves heading back towards town. It wasn't raining today, but clouds had moved in and made the sky oppressively grey, and the wind was cold. Giulia and the boys huddled in the blanket as they transformed back, thin human skins feeling the cold far more keenly than scaly coats adapted for deep water. This time, they knew, they were definitely in trouble. Giulia and Alberto had run off exactly as their parents had told them not to do, and there would be consequences for that... and Luca felt like it was partly his fault, too, since it was him they'd been looking for.

"Papà," said Giulia.

Massimo looked at her, but he still didn't speak.

"I'm sorry we scared you," she said, "but we had to get Luca. He was all by himself."

Her father glanced at Luca, who hunched over and stared at his toes in the bottom of the boat.

"Yes, you did," said Massimo, with a single nod.

The sun was setting by the time they reached the quay below the Pescheria, glaring out from under the clouds like an angry orange eye. It cast long, coal-black shadows across the roofs and streets. A few people were out and about as they always were, although they were keeping close to the buildings in the chilly air. One of them was Old Tommaso, holding on tight to his hat so the chilly wind wouldn't carry it off his head.

Another was Ciccio, standing in the doorway of his father's bakery. He waved eagerly to them as they climbed the steps.

"Giordana doesn't have a boyfriend! I asked her!" he announced.

"Great. Maybe next time you give her a present, you should pick something that won't turn to mush in the water," Alberto called back.

Ciccio got up and came to meet them. "It was the only thing I could think of," he said. "Do you, uh..." he chuckled nervously. "Do you think you could ask her if she's planning to come to town again anytime soon? Don't tell her I told you to, just make it a casual thing..."

Alberto took pity. "She's still here. She and her little brother are staying with Concetta and Pinuccia up the hill."

"Really?" Ciccio asked eagerly.

"Yeah. For a few days, anyway."

"Thanks!" The older boy grinned, and looked for a moment like he might give Alberto a hug before thinking better of it.

"No problem," said Alberto, taking a step backwards just in case. "Good luck."

Massimo herded the kids inside. At the top of the stairs they found Helena in the kitchen, distractedly peeling carrots. She looked up hopefully as they came inside, then quickly put the vegetables aside and crossed the room to gather up all three of them in a tight hug.

"You scared me to death!" she said. "Giulia, I thought you were just going to bring Alberto back. When you didn't come I was terrified you'd both been whisked away the moment you went under the water!"

"I'm sorry, Mamma," Giulia said, "but we had to get Luca."

"I was fine," Luca insisted. "We didn't even see the genie."

Helena loosened her hold and held the three back at arm's length. She could see that Luca's eyes were red. Even if he hadn't been doing it in the same way a human would, it was clear that he'd been crying down there.

"We're going to have a talk about this later," Helena warned, "but for now I'm just glad you're all safe. Wash up and get your warm clothes on, and let's have dinner."

Supper that night was a fish stew, which wasn't among the better human food Luca and Alberto had ever tasted. Helena had left it on the heat for too long, and it had turned out soggy and flavourless. Nobody complained, though - in fact, nobody felt much like talking at all, so the only sounds in the kitchen were the clinking of cutlery on china as everybody ate.

"How is Signor Donzella?" Luca asked, when the quiet got to be too much.

"He's fine," said Helena. "Carolina Marsigliese and I took him up to the hostel while Massimo went back out to look for you three. Signor Gamacchio was glad he didn't also want to sleep in the basement."

Luca nodded, stirring his food around his plate in the hope that nobody would notice he wasn't eating. "We didn't see the genie. I don't know where he went. Maybe he went back to the shipwreck. Maybe he kind of lives there." He shrugged. "I didn't think to check."

"You're definitely not going back out there to look tonight," Helena said firmly. "The weather's getting worse again."

As if on cue, the lights flickered. Everybody looked out the window to see the bare branches of Giulia's tree swaying in the increasingly fierce wind.

Luca kept talking. "Or he might have gone somewhere else," he said, still thinking of the genie. "There are other sea monsters around. I know some live down south near Corsica, because Mom has cousins there. And I've heard there's a bigger settlement off the coast near Pisa, but I've never been there. Grandma has, though. She told me that a lot of human tourists come to Pisa, so the sea monsters there spend more time out of the water because they can blend in with all the strangers."

"I'm sure the genie isn't going to take away all the sea monsters in the entire Mediterranean," Helena assured him.

Luca just shrugged. Who knew what the genie might do? They had no idea what it was trying to accomplish. Maybe it really did just hate sea monsters and had decided to get rid of them, every last one. It did seem to think they were very cruel people, who would do things like kill a human just for wanting to play with them. Or maybe... maybe it was upset that they weren't like it remembered, that they didn't build temples and observatories anymore. Maybe it had taken them to show them the ruins of those things, or to a place where sea monsters did still do things like that, in order to teach them. That was a much nicer idea, but for that reason alone Luca doubted it was true. This didn't seem like the sort of problem that worked out all by itself that way.

"I'm afraid there's no dessert tonight," said Helena as she collected dishes. She noticed that Luca's plate still had most of his dinner on it, but didn't comment.

"That's okay, Mamma," Giulia replied. "We're not very hungry anyway."

"Luca," Alberto said, "where's that amulet? I want to try drawing copies of it."

"I'm still wearing it." Luca found the knot in the twine and tried to untie it, but he'd pulled it so tight he couldn't get his fingernails into it. He had to find the scissors again and cut the string.

Alberto got some paper and a pen, and sat down at the kitchen table to copy out the symbols and the little face. He leaned very close to the paper and put his tongue out as he concentrated, wanting to get it exactly right. Meanwhile Giulia helped her parents with the dishes, as she and Luca had often done in Genova. She'd never paid much attention to the fact that the plates sometimes had enough water on them to make Luca's hands transform – but when hers did it, she found it made things seem much more slippery. She had to be extra careful not to drop anything, but if Luca could do it, she could do it.

"I assume you know why we're upset that you ran off like that," Helena observed, as Giulia stacked the dry plates.

"Yeah." Giulia sighed. "We're the ones who told you it was probably dangerous and then we went anyway."

Helena nodded. "I'm glad you found Luca. You're right that he shouldn't be by himself at a time like this. I just think... we're going to have to plan things a little more carefully. You know you're not alone in this, right?" she asked. "Your father and I want to help if we can."

"We know," said Giulia. She was used to being more or less on her own in Portorosso, because Massimo was usually busy and it was generally a less dangerous place than the big city of Genova. It took an effort to remember that it wasn't just her and the boys now.

While Helena and Giulia did dishes and Massimo repaired a hole in one of his shirts, Luca sat at the table and alternated between watching Alberto draw and looking out the window. It was dark now, with no moon visible, just the dark shapes of tree branches, swaying in the wind in front of the sky and ocean. There were no clouds of glowing plankton up here, and Luca missed them more than ever. There weren't even any stars.

Luca loved the stars. He had first seen them the same night he'd seen his first fire, when Alberto had lit the firepit so the two of them could cook sausages on sticks. He'd asked what they were and Alberto had told him they were anchovies... which had made it seem very strange that they never moved, but made the same shapes night after night. There was on particular group of them in roughly the shape of a fish, which was easy to find because of the one big bright star in the tail. Luca had pointed it out to the astronomy teacher on an observing night, and she'd told him that the group of stars was called Lira, the Harp, and that the bright one was called Vega. It was a very important star, she'd said, because all other stars were measured by how bright they were compared to Vega.

He wondered if he were going to get to go back to school. If his family was gone somebody would have to stay and look after their farm, and the humans definitely couldn't do it...

"I figure," Alberto announced, "we'll go see Professor Hamid again first thing in the morning."

That perked Luca up a little. His friends were still here and they'd promised to help him fix it. He didn't know if he'd be able to figure this out by himself, but with Alberto and Giulia, and Massimo and Helena, all helping they'd have to be able to come up with something.

"She can tell us if we can make more amulets," Alberto went on, "and if we can, all of us can go with your uncle to talk to this Librarian of the Deep."

"And if we can't," Giulia chimed in, "then he can go by himself, and we can give him a list of questions to ask or something."

"Will he be able to read them down there in the dark?" asked Alberto, but then answered his own question. "Of course he will. He's got that glowing thing on his head."

"Like having your own reading light," Giulia agreed. "I bet he misses it." It hadn't occurred to her, but when she thought about it, Luca's uncle would have had that light all his life. For all he claimed to like the dark, he might never have been in total darkness before.

"We'll ask him tomorrow," Alberto decided.

"And if he does, we can loan him my old nightlight," Giulia suggested. She hadn't used it in years.

"That's a good idea," said Helena, "but I think it's also a good idea if you three go to bed early. You've had a long today, and tomorrow's probably going to be another one."

Giulia would normally have argued with this, and she knew Alberto would have, too... but all three of them were exhausted. Luca was in the middle of a yawn even as Helena spoke. There were only token protests as they let Massimo shoo them all up the stairs into Giulia's room.

"Nobody makes Maciste go to bed when he's trying to save the world," Alberto grumbled, referring to the hero of a couple of movies he'd seen.

Luca didn't answer, and just let himself flop forward onto Giulia's bed. It was tempting to just lie there and go to sleep with all his clothes on, but he knew that wasn't how humans did things. He made himself brush his teeth and put his pajamas on, then crawled inside his sleeping bag.

"I wonder where my Dad is," Alberto said suddenly.

Luca opened his eyes, but didn't say anything. He could see Giulia reaching for the light switch, but neither she nor Alberto realized Luca was still awake.

"You told Signor Donzella you didn't care," Giulia said.

"I don't," Alberto replied quickly. "I just wondered if the genie found him, that's all."

"I dunno," said Giulia. "Guess we'll find out."

Darkness fell, and Luca closed his eyes again. A moment ago he'd felt like he was going to sleep like a lungfish hibernating in the mud, completely dead to the world. Now, he wondered if he were going to be able to sleep at all.

Luca did sleep, but not well – he would wake up over and over and remember what had happened, and would curl up miserably in his sleeping bag. When he'd been little and woke up from the occasional nightmare, he'd used to wrap his tail around himself like a hug. He couldn't do that in human form, so he just twisted up an extra blanket Giulia's parents had provided, and clutched that until he fell asleep again.

Giulia didn't get much sleep, either, having a series of dreams about turning into a sea monster at inopportune moments. In the morning, however, there was no time for sitting around being tired. All three feigned wakefulness as best they could, and had a quick breakfast of coffee and foccacia before heading up the hill to the hostel. It was doubly nice, Giulia thought, that Signor Gamacchio had offered to let displaced sea monsters stay with him, because it meant they could talk to Professor Hamid and check in on Luca's uncle and Signor Donzella, all in one stop.

When they arrived, they found the shop was already open. A man was standing outside reading the day's paper, and he nodded at the kids as they opened the door. Inside, they found a chess board on the counter with a game in progress, but only one player. This was Uncle Ugo, leaning on the counter and studying the board. Somebody had persuaded him to put human clothes on, consisting of a grey polo shirt with a green stripe and a pair of shorts that would have been far better suited to June than December.

"Good morning, children," he said to them. "Come to rescue me?"

"Was it that bad?" asked Luca, worried.

"Far, far too much oxygen up here," Uncle Ugo replied, thumping on his chest as if he had a bad cough. "Makes my head spin."

"Was it too dark in the basement?" Giulia wanted to know. "I've got a nightlight you could borrow."

"No, no... the dark was fine," said Ugo. "It was nice and damp, too, and there were these lovely little creatures to keep me company. Don't know what they're called, but they scuttle like crabs and their eyes glow red like the fish in the Deep." He smiled. "They curled up to sleep right next to me. Made me feel very welcome, yes."

Nobody else was smiling. "Those are rats, Uncle Ugo," Luca said. "Nobody likes them."

"I found them very charming," said Ugo. "Not much meat on them, though."

This statement was followed by a horrified silence, but before it could get too awkward, Signor Gamacchio came back downstairs, with Donzella behind him. The blacksmith must have eventually figured out how to walk, but he clearly did not like the steep staircase, and had his hands on his host's shoulders for support.

"Buongiorno!" the kids chorused, eager to change the subject.

"How'd you sleep?" Luca added.

"Not a wink," Signor Donzella replied, heaving himself into a chair while Signor Gamacchio returned to behind the counter and considered his next chess move. Donzella was dressed today, too, in beige trousers and a blue button-down shirt, both a little small on him. His injured thumb had been put in a splint. "Heck of a sensation, gravity. I felt like I had a great big flounder settled down on top of me."

"I bet," said Giulia. "The first time I slept underwater, at Luca's house, I kept feeling like I was falling out of bed. It's gotta be just as weird going the other way, too."

It was only after this popped out that she remembered they hadn't been going to tell people about her. The statement earned her a puzzled look from Signor Gamacchio, and Donzella leaned forward, interested. "So that's why I hadn't met you before. You live up here, like that old couple? I had no idea so many people did that."

Giulia hurriedly changed the subject. "How's your thumb?" she asked, pointing.

At the same time, Luca also tried to distract everybody. "Signor Gamacchio," he said, "can we speak to Professor Hamid?"

Donzella looked at his hand. "It doesn't hurt as much. Your doctor gave me something to swallow for the pain and it worked a treat, though it doesn't taste as nice as the stuff Chiara would have given me. He says I can't get the plaster wet, though, which is gonna be a problem."

Signor Gamacchio moved a knight. "The Professor?" he said to Alberto. "You missed her. She left ten minutes ago to catch her train."

The atmosphere in the room changed in a heartbeat. "She's leaving?" Luca asked.

"Yes," said Signor Gamacchio, watching Uncle Ugo move a pawn. "She said she was due back in Napoli for..."

"Excuse us!" Luca turned and darted out of the shop. Alberto and Giulia offered apologetic smiles and ran after him.

If Professor Hamid had been going to Genova, Giulia would have known exactly which train she would be taking and how much time they had before it left, but she had never even thought about how to get to Napoli. All they could do was run across town as fast as they could and arrive panting at the station. There, to their relief, they found the Professor had not left yet. She was standing on the platform, waiting with her bags.

"Professor!" Luca called out.

"Oh. Hello, kids," she said with a slightly forced smile, raising a had to wave to them. "Come to say goodbye?"

"No, we need to ask you some more things," Luca said, pausing to lean on the brick wall and catch his breath.

Alberto pulled out his drawing from last night. "Will this work as another amulet, or does it need to be the whole thing, made of gold and everything?"

"And what else do you know about genies?" was Luca's question.

Professor Hamid looked them over with a puzzled frown. "Genies?" she echoed.

Luca nodded. "It's an emergency," he said.

The Professor stood there quietly for a moment, then said, "you know, I swear to you, I don't normally go around inquiring about other people's business... but what is going on in this town?"

The only thing they could do was tell the truth, and all three of them knew it. There wasn't time to come up with another explanation for why they needed to know these things right now, if they could have figured one out at all.

"There was another bottle I found in the shipwreck," Alberto said. "It had a genie in it."

"And I made a wish," Giulia added. "The genie granted it and then he vanished, and now he's going around making people disappear and we don't know why."

"My uncle was okay because he had the amulet," Luca said, "but my parents and grandmother are gone and we have to figure out how to get them back. Please, anything you could tell us would be great."

The Professor blinked. "That's... that's it?" she asked. "All this is just a game that got out of hand?"

"It's not a game!" the kids said, in indignant unison.

She sighed and shook her head. "I don't have time for this. My train will be here any moment. In fact..." the Professor checked her watch. "It should have been here already." She sounded like she couldn't wait to leave this peculiar little corner of her adopted country. "Genies aren't real, especially the kind who live in bottles and grant wishes. You're all old enough that you should know that... aren't you?"

"It's true, though," Luca insisted.

"Why would we tell you that if it wasn't true?" Alberto asked.

Giulia recalled what her mother had said to Concetta and Pinuccia, and wondered if that might help them now. "Sea monsters are real!" she announced. "If sea monsters exist, then genies can, too, right? If we show you a sea monster, will you believe in a genie?"

She was terrified the answer would be another dismissal. If Professor Hamid wouldn't help them, then all they would have would be the Library of the Deep. The only one who knew the way there was Uncle Ugo, and if they let him go alone, they were a little afraid he wouldn't come back.

The Professor shut her eyes a moment, as if feeling a headache coming on, but then opened them again. "All right," she said, having decided to humour the kids. "Show me a sea monster."

They heard a train whistle, and realized they had only a minute or so to do it. "We need water," said Giulia.

"The fire hose!" Luca pointed to it, hanging in a coil on the wall. He and Giulia ran to get it down, while Alberto put all his might into turning the spigot. At first it wouldn't budge, but then, with a squeak of unoiled metal, it moved a tiny bit, and the hose began to fill. Alberto gritted his teeth and gave it another twist that almost made his fingers to numb, and water came bursting out.

It was a lot colder, and a lot more powerful, than any of the three expected, but it did get them very effectively soaked. Dripping and shivering, three small sea monsters dropped the hose and turned to face Professor Hamid.

They tried to prepare themselves for any possible reaction, from a terrified scream to simple frozen, shocked silence. At first they seemed to be getting the latter, as the Professor stared at them with her eyes and mouth wide open. Then, slowly, she raised a trembling finger to point at them and managed to word, "apkallu!"

None of them knew what that meant, whether it was a name or a curse or perhaps something protective like the spell on the back of the amulet. Nor did they get a chance to ask, because moments later, the train began pulling into the station. Most of the people on board were only passing through Portorosso, and had no idea of the town's relationship with its unique aquatic neighbours. Any one of them could be the sort of person they didn't want knowing about sea monsters.

"Gotta run!" Alberto grabbed his friends' arms and dragged them into the station building, where they wrenched a door open and piled into the janitors' closet, much to the surprise of the woman in the ticket booth. With the door closed behind them, it was stuffy and dark, and there was barely room for all three of them.

Giulia's foot came down on something she at first assumed was a piece of hose, until she felt it twitch.

"Ow!" whispered Alberto. "Who's on my tail?"

"Sorry! That's me!" Giulia moved to get off of it, and accidentally put her elbow in Luca's face.

"Hey!" he complained.

"Sssssh!" Alberto said.

The train hissed and groaned as it pulled up to the platform, its bell ringing, but that wasn't quite enough to drown out the sound of Professor Hamid shouting for them to come back. Her footsteps came hurrying into the room.

"Excuse me!" she said to the ticket lady. "I was talking to three little, uh... creatures..."

"Sea monsters," the woman finished for her, as if this were nothing strange. "They're in the closet."

"Thank you!"

"Wait, wait," the ticket lady said. "People are getting off the train. Give them a moment to dry out."

More voices and footsteps could be heard as the train passengers got on and off. Wheels squeaked on luggage trollies and conversations happened, and as the minutes passed, the kids began to worry.

"Signor Gamacchio said she had somewhere to go," said Luca. "What if she just leaves? This wasn't a good plan."

"This wasn't really a plan at all," Alberto grumbled.

"Sorry. Probably could have timed it better," Giulia said. She hadn't had a single good idea since this all started, had she?

They waited a few minutes more, and the hubbub began to die down.

"Okay. Everybody look human?" asked Alberto.

"Yeah," said Giulia, reaching up to tug on her hair just to be sure.

"I think so," said Luca. Giulia felt him moving around next to her, and then his hand grabbed at her arm.

"Hey! What are you doing?" she whispered.

"I'm checking for my tail!" he replied. "I can never feel if it's gone or not."

"Was you guys' entire summer like this?" Giulia asked.

"Pretty much, yeah," said Luca.

Alberto cracked the door open the peek out, and then opened it further. Professor Hamid was waiting outside. The kids smiled awkwardly at her.

"Hi," said Alberto.

"Hello," she replied, looking dazed. "So, uh... the whole town...?"

"No, no, no," said Luca quickly.

"Just us," Giulia agreed.

"And the two old ladies," Alberto said. "They're Giordana and Arturo's great aunts... I think."

"Giordana and Arturo too," Luca put in, "and my uncle of course."

Professor Hamid seemed to have worked out the pattern. "Everybody who goes around dressed in woven grass," she said, and looked at Giulia. "And your parents, I presume."

"No, Massimo and Helena are humans," said Alberto.

"Alberto's adopted," Giulia explained, "and I'm... that's what I wished for. From the genie. Because they're my friends and they had all this stuff planned to do underwater where I couldn't go, so I wished I was a sea monster, too."

"And she's a natural at it," Alberto said loyally.

The train whistle sounded outside and a voice shouted, "all aboard!" Professor Hamid turned to look out at the platform, then back at the three kids.

"Now the genie's making people disappear, and we don't know how to get them back," Luca repeated. "My Mom, my Dad, my Grandma..."

"Arturo and Giordana's Mom," Alberto said, "and Signor Donzella's wife and son. All our neighbours, everybody. We need somebody who knows what to do about genies."

The Professor shook her head. "I don't know much about them beyond the stories from The Thousand and One Nights. We didn't talk about things like that in our house because my family are Christians, and the church considers djinn to be demons."

Giulia and the boys all felt themselves wilt a little.

"But," the Professor held up a finger. "I know somebody we can ask. Is there a public telephone?"