The problem was, it had been so long since Leo had had a family, he couldn’t even remember how it felt. Sure, last winter he’d become senior counselor of Hephaestus cabin; but most of his time had been spent building the ship. He liked his cabin mates. He knew how to work with them—but did he really know them?

If Leo had a family, it was the demigods on the Argo II—and maybe Coach Hedge, which Leo would never admit aloud.

You will always be the outsider, warned Nemesis’s voice; but Leo tried to push that thought aside.

“Right, so…” He looked around him. “We need to make a plan. How are we breathing? If we’re under the ocean, shouldn’t we be crushed by the water pressure?”

Frank shrugged. “Fish-horse magic, I guess. I remember the green guy touching my head with the point of a dagger. Then I could breathe.”

Leo studied the abalone door. “Can you bust us out? Turn into a hammerhead shark or something?”

Frank shook his head glumly. “My shape-shifting doesn’t work. I don’t know why. Maybe they cursed me, or maybe I’m too messed up to focus.”

“Hazel could be in trouble,” Leo said. “We’ve got to get out of here.”

He swam to the door and ran his fingers along the abalone. He couldn’t feel any kind of latch or other mechanism. Either the door could only be opened by magic or sheer force was required—neither of which was Leo’s specialty.

“I’ve already tried,” Frank said. “Even if we get out, we have no weapons.”

“Hmm…” Leo held up his hand. “I wonder.”

He concentrated, and fire flickered over his fingers. For a split second, Leo was excited, because he hadn’t expected it to work underwater. Then his plan started working a little too well. Fire raced up his arm and over his body until he was completely shrouded in a thin veil of flame. He tried to breathe, but he was inhaling pure heat.

“Leo!” Frank flailed backward like he was falling off a bar stool. Instead of racing to Leo’s aid, he hugged the wall to get as far away as possible.

Leo forced himself to stay calm. He understood what was going on. The fire itself couldn’t hurt him. He willed the flames to die and counted to five. He took a shallow breath. He had oxygen again.

Frank stopped trying to merge with the cave wall. “You’re…you’re okay?”

“Yeah,” Leo grumbled. “Thanks for the assist.”

“I—I’m sorry.” Frank looked so horrified and ashamed it was hard for Leo to stay mad at him. “I just…what happened?”

“Clever magic,” Leo said. “There’s a thin layer of oxygen around us, like an extra skin. Must be self-regenerating. That’s how we’re breathing and staying dry. The oxygen gave the fire fuel—except the fire also suffocated me.”

“I really don’t…” Frank gulped. “I don’t like that fire summoning you do.” He started getting cozy with the wall again.

Leo didn’t mean to, but he couldn’t help laughing. “Man, I’m not going to attack you.”

“Fire,” Frank repeated, like that one word explained everything.

Leo remembered what Hazel had said—that his fire made Frank nervous. He’d seen the discomfort in Frank’s face before, but Leo hadn’t taken it seriously. Frank seemed way more powerful and scary than Leo was.

Now it occurred to him that Frank might have had a bad experience with fire. Leo’s own mom had died in a machine shop blaze. Leo had been blamed for it. He’d grown up being called a freak, an arsonist, because whenever he got angry, things burned.

“Sorry I laughed,” he said, and he meant it. “My mom died in a fire. I understand being afraid of it. Did, uh…did something like that happen with you?”

Frank seemed to be weighing how much to say. “My house…my grandmother’s place. It burned down. But it’s more than that…” He stared at the sea urchins on the floor. “Annabeth said I could trust the crew. Even you.”

“Even me, huh?” Leo wondered how that had come up in conversation. “Wow, high praise.”

“My weakness…” Frank started, like the words cut his mouth. “There’s this piece of firewood—”

The abalone door rolled open.

Leo turned and found himself face-to-face with Lima Bean Man, who wasn’t actually a man at all. Now that Leo could see him clearly, the guy was by far the weirdest creature he’d ever met, and that was saying a lot.

From the waist up, he was more or less human—a thin, bare-chested dude with a dagger in his belt and a band of seashells strapped across his chest like a bandolier. His skin was green, his beard scraggly brown, and his longish hair was tied back in a seaweed bandana. A pair of lobster claws stuck up from his head like horns, turning and snapping at random.

Leo decided he didn’t look so much like Chiron. He looked more like the poster Leo’s mom used to keep in her workspace—that old Mexican bandit Pancho Villa, except with seashells and lobster horns.

From the waist down, the guy was more complicated. He had the forelegs of a blue-green horse, sort of like a centaur, but toward the back, his horse body morphed into a long fishy tail about ten feet long, with a rainbow-colored, V-shaped tail fin.

Now Leo understood what Frank meant about fish-horse guys.

“I am Bythos,” said the green man. “I will interrogate Frank Zhang.”

His voice was calm and firm, leaving no room for debate.

“Why did you capture us?” Leo demanded. “Where’s Hazel?”

Bythos narrowed his eyes. His expression seemed to say: Did this tiny creature just talk to me? “You, Leo Valdez, will go with my brother.”

“Your brother?”

Leo realized that a much larger figure was looming behind Bythos, with a shadow so wide, it filled the entire cave entrance.

“Yes,” Bythos said with a dry smile. “Try not to make Aphros mad.”

Chapter 24

Aphros looked like his brother, except he was blue instead of green and much, much bigger. He had Arnold-as-Terminator abs and arms, and a square, brutish head. A huge Conan-approved sword was strapped across his back. Even his hair was bigger—a massive globe of blue-black frizz so thick that his lobster-claw horns appeared to be drowning as they tried to swim their way to the surface.

“Is that why they named you Aphros?” Leo asked as they glided down the path from the cave. “Because of the Afro?”

Aphros scowled. “What do you mean?”

“Nothing,” Leo said quickly. At least he would never have trouble remembering which fish dude was which. “So what are you guys, exactly?”

“Ichthyocentaurs,” Aphros said, like it was a question he was tired of answering.

“Uh, icky what?”

“Fish centaurs. We are the half brothers of Chiron.”

“Oh, he’s a friend of mine!”

Aphros narrowed his eyes. “The one called Hazel told us this, but we will determine the truth. Come.”

Leo didn’t like the sound of determine the truth. It made him think of torture racks and red-hot pokers.

He followed the fish centaur through a massive forest of kelp. Leo could’ve darted to one side and gotten lost in the plants pretty easily, but he didn’t try. For one thing, he figured Aphros could travel much faster in the water, and the guy might be able to shut off the magic that let Leo move and breathe. Inside or outside the cave, Leo was just as much a captive.

Also, Leo had no clue where he was.

They drifted between rows of kelp as tall as apartment buildings. The green-and-yellow plants swayed weightlessly, like columns of helium balloons. High above, Leo saw a smudge of white that might have been the sun.

He guessed that meant they’d been here overnight. Was the Argo II all right? Had it sailed on without them, or were their friends still searching?

Leo couldn’t even be sure how deep they were. Plants could grow here—so not too deep, right? Still, he knew he couldn’t just swim for the surface. He’d heard about people who ascended too quickly and developed nitrogen bubbles in their blood. Leo wanted to avoid carbonated blood.

They drifted along for maybe half a mile. Leo was tempted to ask where Aphros was taking him, but the big sword strapped to the centaur’s back sort of discouraged conversation.

Finally the kelp forest opened up. Leo gasped. They were standing (swimming, whatever) at the summit of a high underwater hill. Below them stretched an entire town of Greek-style buildings on the seafloor.

The roofs were tiled with mother-of-pearl. The gardens were filled with coral and sea anemones. Hippocampi grazed in a field of seaweed. A team of Cyclopes was placing the domed roof on a new temple, using a blue whale as a crane. And swimming through the streets, hanging out in the courtyards, practicing combat with tridents and swords in the arena were dozens of mermen and mermaids—honest-to-goodness fish-people.

Leo had seen a lot of crazy stuff, but he had always thought merpeople were silly fictional creatures, like Smurfs or Muppets.

There was nothing silly or cute about these merpeople, though. Even from a distance, they looked fierce and not at all human. Their eyes glowed yellow. They had sharklike teeth and leathery skin in colors ranging from coral red to ink black.

“It’s a training camp,” Leo realized. He looked at Aphros in awe. “You train heroes, the same way Chiron does?”

Aphros nodded, a glint of pride in his eyes. “We have trained all the famous mer-heroes! Name a mer-hero, and we have trained him or her!”

“Oh, sure,” Leo said. “Like…um, the Little Mermaid?”

Aphros frowned. “Who? No! Like Triton, Glaucus, Weissmuller, and Bill!”

“Oh.” Leo had no idea who any of those people were. “You trained Bill? Impressive.”

“Indeed!” Aphros pounded his chest. “I trained Bill myself. A great merman.”

“You teach combat, I guess.”

Aphros threw up his hands in exasperation. “Why does everyone assume that?”

Leo glanced at the massive sword on the fish-guy’s back. “Uh, I don’t know.”

“I teach music and poetry!” Aphros said. “Life skills! Homemaking! These are important for heroes.”

“Absolutely.” Leo tried to keep a straight face. “Sewing? Cookie baking?”

“Yes. I’m glad you understand. Perhaps later, if I don’t have to kill you, I will share my brownie recipe.” Aphros gestured behind him contemptuously. “My brother Bythos—he teaches combat.”

Leo wasn’t sure whether he felt relieved or insulted that the combat trainer was interrogating Frank, while Leo got the home economics teacher. “So, great. This is Camp…what do you call it? Camp Fish-Blood?”

Aphros frowned. “I hope that was a joke. This is Camp __________.” He made a sound that was a series of sonar pings and hisses.

“Silly me,” Leo said. “And, you know, I could really go for some of those brownies! So what do we have to do to get to the not killing me stage?”