In one aquarium, a dozen hippocampi—horses with the tails of fish—drifted aimlessly. Percy had seen many hippocampi in the wild. He’d even ridden a few; but he had never seen any in an aquarium. He tried to speak with them, but they just floated around, occasionally bonking against the glass. Their minds seemed addled.

“This isn’t right,” Percy muttered.

He turned and saw something even worse. At the bottom of a smaller tank, two Nereids—female sea spirits—sat cross-legged, facing each other, playing a game of Go Fish. They looked incredibly bored. Their long green hair floated listlessly around their faces. Their eyes were half closed.

Percy felt so angry, he could hardly breathe. He glared at Kate. “How can you keep them here?”

“I know.” Kate sighed. “They aren’t very interesting. We tried to teach them some tricks, but with no luck, I’m afraid. I think you’ll like this tank over here much better.”

Percy started to protest, but Kate had already moved on.

“Holy mother of goats!” cried Coach Hedge. “Look at these beauties!”

He was gawking at two sea serpents—thirty-foot-long monsters with glowing blue scales and jaws that could have bitten a whale shark in half. In another tank, peeking out from its cement cave, was a squid the size of an eighteen-wheeler, with a beak like a giant bolt cutter.

A third tank held a dozen humanoid creatures with sleek seal bodies, doglike faces, and human hands. They sat on the sand at the bottom of the tank, building things out of Legos, though the creatures seemed just as dazed as the Nereids.

“Are those—?” Percy struggled to form the question.

“Telkhines?” Kate said. “Yes! The only ones in captivity.”

“But they fought for Kronos in the last war!” Percy said. “They’re dangerous!”

Kate rolled her eyes. “Well, we couldn’t call it ‘Death in the Deep Seas’ if these exhibits weren’t dangerous. Don’t worry. We keep them well sedated.”

“Sedated?” Frank asked. “Is that legal?”

Kate appeared not to have heard. She kept walking, pointing out other exhibits. Percy looked back at the telkhines. One was obviously a youngster. He was trying to make a sword out of Legos, but he seemed too groggy to put the pieces together. Percy had never liked sea demons, but now he felt sorry for them.

“And these sea monsters,” Kate narrated up ahead, “can grow five hundred feet long in the deep ocean. They have over a thousand teeth. And these? Their favorite food is demigod—”

“Demigod?” Frank yelped.

“But they will eat whales or small boats, too.” Kate turned to Percy and blushed. “Sorry…I’m such a monster nerd! I’m sure you know all this, being the son of Poseidon, and all.”

Percy’s ears were ringing like alarm bells. He didn’t like how much Kate knew about him. He didn’t like the way she casually tossed out information about drugging captive creatures or which of her babies liked to devour demigods.

“Who are you?” he demanded. “Does Kate stand for something?”

“Kate?” She looked momentarily confused. Then she glanced at her name tag. “Oh…” She laughed. “No, it’s—”

“Hello!” said a new voice, booming through the aquarium.

A small man scuttled out of the darkness. He walked sideways on bowed legs like a crab, his back hunched, his arms raised on either side like he was holding invisible plates.

He wore a wet suit that was several horrible shades of green. Glittery silver words printed down the side read: PORKY’S FOLLIES. A headset microphone was clamped over his greasy wiry hair. His eyes were milky blue, one higher than the other, and though he smiled, he didn’t look friendly—more like his face was being peeled back in a wind tunnel.

“Visitors!” the man said, the word thundering through the microphone. He had a DJ’s voice, deep and resonant, which did not at all match his appearance. “Welcome to Phorcys’s Follies!”

He swept his arms in one direction, as if directing their attention to an explosion. Nothing happened.

“Curse it,” the man grumbled. “Telkhines, that’s your cue! I wave my hands, and you leap energetically in your tank, do a synchronized double spin, and land in pyramid formation. We practiced this!”

The sea demons paid him no attention.

Coach Hedge leaned toward the crab man and sniffed his glittery wet suit. “Nice outfit.”

He didn’t sound like he was kidding. Of course, the satyr wore gym uniforms for fun.

“Thank you!” The man beamed. “I am Phorcys.”

Frank shifted his weight from foot to foot. “Why does your suit say Porky?”

Phorcys snarled. “Stupid uniform company! They can’t get anything right.”

Kate tapped her name tag. “I told them my name was Keto. They misspelled it as Kate. My brother…well, now he’s Porky.”

“I am not!” the man snapped. “I’m not even a little porky. The name doesn’t work with Follies, either. What kind of show is called Porky’s Follies? But you folks don’t want to hear us complain. Behold, the wondrous majesty of the giant killer squid!”

He gestured dramatically toward the squid tank. This time, fireworks shot off in front of the glass right on cue, sending up geysers of golden sparkles. Music swelled from the loudspeakers. The lights brightened and revealed the wondrous majesty of an empty tank.

The squid had apparently skulked back into its cave.

“Curse it!” Phorcys yelled again. He wheeled on his sister. “Keto, training the squid was your job. Juggling, I said. Maybe a bit of flesh-rending for the finale. Is that too much to ask?”

“He’s shy,” Keto said defensively. “Besides, each of his tentacles has sixty-two razorlike barbs that have to be sharpened daily.” She turned toward Frank. “Did you know the monstrous squid is the only beast known to eat demigods whole, armor and all, without getting indigestion? It’s true!”

Frank stumbled away from her, hugging his gut as if making sure he was still in one piece.

“Keto!” Porky snapped—literally, since he clicked his fingers to his thumbs like crab claws. “You’ll bore our guests with so much information. Less education, more entertainment! We’ve discussed this.”

“But—”

“No buts! We’re here to present ‘Death in the Deep Seas!’ Sponsored by Monster Donut!”

The last words reverberated through the room with extra echo. Lights flashed. Smoke clouds billowed from the floor, making donut-shaped rings that smelled like real donuts.

“Available at the concession stand,” Phorcys advised. “But you’ve spent your hard-earned denarii to get the VIP tour, and so you shall! Come with me!”

“Um, hold it,” Percy said.

Phorcys’s smile melted in an ugly way. “Yes?”

“You’re a sea god, aren’t you?” Percy asked. “Son of Gaea?”

The crab man sighed. “Five thousand years, and I’m still known as Gaea’s little boy. Never mind that I’m one of the oldest sea gods in existence. Older than your upstart father, by the way. I’m god of the hidden depths! Lord of watery terrors! Father of a thousand monsters! But, no…nobody even knows me. I make one little mistake, supporting the Titans in their war, and I’m exiled from the ocean—to Atlanta, of all places.”

“We thought the Olympians said Atlantis,” Keto explained. “Their idea of a joke, I guess, sending us here instead.”

Percy narrowed his eyes. “And you’re a goddess?”

“Keto, yes!” She smiled happily. “Goddess of sea monsters, naturally! Whales, sharks, squids, and other giant sea life, but my heart always belonged to the monsters. Did you know that young sea serpents can regurgitate the flesh of their victims and keep themselves fed for up to six years on the same meal? It’s true!”

Frank was still clutching his stomach like he was going to be sick.

Coach Hedge whistled. “Six years? That’s fascinating.”

“I know!” Keto beamed.

“And how exactly does a killer squid rend the flesh from its victims?” Hedge asked. “I love nature.”

“Oh, well—”

“Stop!” Phorcys demanded. “You’re ruining the show! Now, witness our Nereid gladiators fight to the death!”

A mirrored disco ball descended into the Nereid exhibit, making the water dance with multicolored light. Two swords fell to the bottom and plunked in the sand. The Nereids ignored them and kept playing Go Fish.

“Curse it!” Phorcys stomped his legs sideways.

Keto grimaced at Coach Hedge. “Don’t mind Porky. He’s such a windbag. Come with me, my fine satyr. I’ll show you full-color diagrams of the monsters’ hunting habits.”

“Excellent!”

Before Percy could object, Keto led Coach Hedge away through a maze of aquarium glass, leaving Frank and him alone with the crabby sea god.

A bead of sweat traced its way down Percy’s neck. He exchanged a nervous look with Frank. This felt like a divide-and-conquer strategy. He didn’t see any way the encounter was going to end well. Part of him wanted to attack Phorcys now—at least that might give them the element of surprise—but they hadn’t found out any useful information yet. Percy wasn’t sure he could find Coach Hedge again. He wasn’t even sure he could find the exit.

Phorcys must’ve read his expression.

“Oh, it’s fine!” the god assured him. “Keto might be a little boring, but she’ll take good care of your friend. And honestly, the best part of the tour is still to come!”

Percy tried to think, but he was starting to get a headache. He wasn’t sure if it was from yesterday’s head injury, Phorcys’s special effects, or his sister’s lectures on nauseating sea monster facts. “So…” he managed. “Dionysus sent us here.”

“Bacchus,” Frank corrected.

“Right.” Percy tried to keep his annoyance in check. He could barely remember one name for each god. Two was pushing it. “The wine god. Whatever.” He looked at Phorcys. “Bacchus said you might know what your mom Gaea is up to, and these twin giant brothers of yours—Ephialtes and Otis. And if you happen to know anything about this Mark of Athena—”

“Bacchus thought I would help you?” Phorcys asked.

“Well, yeah,” Percy said. “I mean, you’re Phorcys. Everybody talks about you.”

Phorcys tilted his head so that his mismatched eyes almost lined up. “They do?”

“Of course. Don’t they, Frank?”

“Oh…sure!” Frank said. “People talk about you all the time.”

“What do they say?” the god asked.

Frank looked uncomfortable. “Well, you have great pyrotechnics. And a good announcer’s voice. And, um, a disco ball—”

“It’s true!” Phorcys clacked his fingers and thumbs excitedly. “I also have the largest collection of captive sea monsters in the world!”