“Percy!” Annabeth said. “Can you talk to that thing? Do you know what it is?”

The son of the sea god shook his head, clearly mystified. “Maybe it’s just curious about the ship. Maybe—”

The monster’s tendrils lashed across the deck so fast, Leo didn’t even have time to yell, Look out!

One slammed Percy in the chest and sent him crashing down the steps. Another wrapped around Piper’s legs and dragged her, screaming, toward the rail. Dozens more tendrils curled around the masts, encircling the crossbows and ripping down the rigging.

“Nose-hair attack!” Hedge snatched up his bat and leaped into action; but his hits just bounced harmlessly off the tendrils.

Jason drew his sword. He tried to free Piper, but he was still weak. His gold blade cut through the tendrils with no problem, but faster than he could sever them, more took their place.

Annabeth unsheathed her dagger. She ran through the forest of tentacles, dodging and stabbing at whatever target she could find. Frank pulled out his bow. He fired over the side at the creature’s body, lodging arrows in the chinks of its shell; but that only seemed to annoy the monster. It bellowed, and rocked the ship. The mast creaked like it might snap off.

They needed more firepower, but they couldn’t use ballistae. They needed to deliver a blast that wouldn’t destroy the ship. But how… ?

Leo’s eyes fixed on a supply crate next to Hazel’s feet.

“Hazel!” he yelled. “That box! Open it!”

She hesitated, then saw the box he meant. The label read WARNING. DO NOT OPEN.

“Open it!” Leo yelled again. “Coach, take the wheel! Turn us toward the monster, or we’ll capsize.”

Hedge danced through the tentacles with his nimble goat hooves, smashing away with gusto. He bounded toward the helm and took the controls.

“Hope you got a plan!” he shouted.

“A bad one.” Leo raced toward the mast.

The monster pushed against the Argo II. The deck lurched to forty-five degrees. Despite everyone’s efforts, the tentacles were just too numerous to fight. They seemed able to elongate as much as they wanted. Soon they’d have the Argo II completely entangled. Percy hadn’t appeared from below. The others were fighting for their lives against nose hair.

“Frank!” Leo called as he ran toward Hazel. “Buy us some time! Can you turn into a shark or something?”

Frank glanced over, scowling; and in that moment a tentacle slammed into the big guy, knocking him overboard.

Hazel screamed. She’d opened the supply box and almost dropped the two glass vials she was holding.

Leo caught them. Each was the size of an apple, and the liquid inside glowed poisonous green. The glass was warm to the touch. Leo’s chest felt like it might implode from guilt. He’d just distracted Frank and possibly gotten him killed, but he couldn’t think about it. He had to save the ship.

“Come on!” He handed Hazel one of the vials. “We can kill the monster—and save Frank!”

He hoped he wasn’t lying. Getting to the port rail was more like rock climbing than walking, but finally they made it.

“What is this stuff?” Hazel gasped, cradling her glass vial.

“Greek fire!”

Her eyes widened. “Are you crazy? If these break, we’ll burn the whole ship!”

“Its mouth!” Leo said. “Just chuck it down its—”

Suddenly Leo was crushed against Hazel, and the world turned sideways. As they were lifted into the air, he realized they’d been wrapped together in a tentacle. Leo’s arms were free, but it was all he could do to keep hold of his Greek fire vial. Hazel struggled. Her arms were pinned, which meant at any moment the vial trapped between them might break…and that would be extremely bad for their health.

They rose ten feet, twenty feet, thirty feet above the monster. Leo caught a glimpse of his friends in a losing battle, yelling and slashing at the monster’s nose hairs. He saw Coach Hedge struggling to keep the ship from capsizing. The sea was dark, but in the moonlight he thought he saw a glistening object floating near the monster—maybe the unconscious body of Frank Zhang.

“Leo,” Hazel gasped, “I can’t—my arms—”

“Hazel,” he said. “Do you trust me?”

“No!”

“Me neither,” Leo admitted. “When this thing drops us, hold your breath. Whatever you do, try to chuck your vial as far away from the ship as possible.”

“Why—why would it drop us?”

Leo stared down at the monster’s head. This would be a tough shot, but he had no choice. He raised the vial in his left hand. He pressed his right hand against the tentacle and summoned fire to his palm—a narrowly focused, white-hot burst.

That got the creature’s attention. A tremble went all the way down the tentacle as its flesh blistered under Leo’s touch. The monster raised its maw, bellowing in pain, and Leo threw his Greek fire straight down its throat.

After that, things got fuzzy. Leo felt the tentacle release them. They fell. He heard a muffled explosion and saw a green flash of light inside the giant pink lampshade of the monster’s body. The water hit Leo’s face like a brick wrapped in sandpaper, and he sank into darkness. He clamped his mouth shut, trying not to breathe, but he could feel himself losing consciousness.

Through the sting of the salt water, he thought he saw the hazy silhouette of the ship’s hull above—a dark oval surrounded by a green fiery corona, but he couldn’t tell if the ship was actually on fire.

Killed by a giant shrimp, Leo thought bitterly. At least let the Argo II survive. Let my friends be okay.

His vision began to dim. His lungs burned.

Just as he was about to give up, a strange face hovered over him—a man who looked like Chiron, their trainer back at Camp Half-Blood. He had the same curly hair, shaggy beard, and intelligent eyes—a look somewhere between wild hippie and fatherly professor, except this man’s skin was the color of a lima bean. The man silently held up a dagger. His expression was grim and reproachful, as if to say: Now, hold still, or I can’t kill you properly.

Leo blacked out.

When Leo woke, he wondered if he was a ghost in another flashback, because he was floating weightlessly. His eyes slowly adjusted to the dim light.

“About time.” Frank’s voice had too much reverb, like he was speaking through several layers of plastic wrap.

Leo sat up…or rather he drifted upright. He was underwater, in a cave about the size of a two-car garage. Phosphorescent moss covered the ceiling, bathing the room in a blue-and-green glow. The floor was a carpet of sea urchins, which would have been uncomfortable to walk on, so Leo was glad he was floating. He didn’t understand how he could be breathing with no air.

Frank levitated nearby in meditation position. With his chubby face and his grumpy expression, he looked like a Buddha who’d achieved enlightenment and wasn’t thrilled about it.

The only exit to the cave was blocked by a massive abalone shell—its surface glistening in pearl and rose and turquoise. If this cave was a prison, at least it had an awesome door.

“Where are we?” Leo asked. “Where is everyone else?”

“Everyone?” Frank grumbled. “I don’t know. As far as I can tell, it’s just you and me and Hazel down here. The fish-horse guys took Hazel about an hour ago, leaving me with you.”

Frank’s tone made it obvious he didn’t approve of those arrangements. He didn’t look injured, but Leo realized that he no longer had his bow or quiver. In a panic, Leo patted his waist. His tool belt was gone.

“They searched us,” Frank said. “Took anything that could be a weapon.”

“Who?” Leo demanded. “Who are these fish-horse—?”

“Fish-horse guys,” Frank clarified, which wasn’t very clear. “They must have grabbed us when we fell in the ocean and dragged us…wherever this is.”

Leo remembered the last thing he’d seen before he passed out—the lima-bean-colored face of the bearded man with the dagger. “The shrimp monster. The Argo II—is the ship okay?”

“I don’t know,” Frank said darkly. “The others might be in trouble or hurt, or—or worse. But I guess you care more about your ship than your friends.”

Leo felt like his face had just hit the water again. “What kind of stupid thing—?”

Then he realized why Frank was so angry: the flashback. Things had happened so fast with the monster attack, Leo had almost forgotten. Coach Hedge had made that stupid comment about Leo and Hazel holding hands and gazing into each other’s eyes. It probably hadn’t helped that Leo had gotten Frank knocked overboard right after that.

Suddenly Leo found it hard to meet Frank’s gaze.

“Look, man…I’m sorry I got us into this mess. I totally jacked things up.” He took a deep breath, which felt surprisingly normal, considering he was underwater. “Me and Hazel holding hands…it’s not what you think. She was showing me this flashback from her past, trying to figure out my connection with Sammy.”

Frank’s angry expression started to unknot, replaced by curiosity. “Did she…did you figure it out?”

“Yeah,” Leo said. “Well, sort of. We didn’t get a chance to talk about it afterward because of Shrimpzilla, but Sammy was my great-grandfather.”

He told Frank what they’d seen. The weirdness hadn’t fully registered yet, but now, trying to explain it aloud, Leo could hardly believe it. Hazel had been sweet on his bisabuelo, a guy who had died when Leo was a baby. Leo hadn’t made the connection before, but he had a vague memory of older family members calling his grandfather Sam Junior. Which meant Sam Senior was Sammy, Leo’s bisabuelo. At some point, Tía Callida—Hera herself—had talked with Sammy, consoling him and giving him a glimpse into the future, which meant that Hera had been shaping Leo’s life generations before he was even born. If Hazel had stayed in the 1940s, if she’d married Sammy, Leo might’ve been her great-grandson.

“Oh, man,” Leo said when he had finished the story. “I don’t feel so good. But I swear on the Styx, that’s what we saw.”

Frank had the same expression as the monster catfish head—wide glassy eyes and an open mouth. “Hazel…Hazel liked your great-grandfather? That’s why she likes you?”

“Frank, I know this is weird. Believe me. But I don’t like Hazel—not that way. I’m not moving in on your girl.”

Frank knit his eyebrows. “No?”

Leo hoped he wasn’t blushing. Truthfully, he had no idea how he felt about Hazel. She was awesome and cute, and Leo had a weakness for awesome cute girls. But the flashback had complicated his feelings a lot.

Besides, his ship was in trouble.

I guess you care more about your ship than your friends, Frank had said.

That wasn’t true, was it? Leo’s dad, Hephaestus, had admitted once that he wasn’t good with organic life forms. And, yes, Leo had always been more comfortable with machines than people. But he did care about his friends. Piper and Jason…he’d known them the longest, but the others were important to him too. Even Frank. They were like family.