Annabeth nodded, still in a daze. The yellow dust dissipated on the rocky shore, turning to steam. At least now they knew monsters could be killed in Tartarus…though she had no idea how long Arachne would remain dead. Annabeth didn’t plan on staying long enough to find out.

“Yeah, downstream,” she managed. “If the river comes from the upper levels of the Underworld, it should flow deeper into Tartarus—”

“So it leads into more dangerous territory,” Percy finished. “Which is probably where the Doors are. Lucky us.”

THEY’D ONLY TRAVELED a few hundred yards when Annabeth heard voices.

Annabeth plodded along, half in a stupor, trying to form a plan. Since she was a daughter of Athena, plans were supposed to be her specialty; but it was hard to strategize with her stomach growling and her throat baking. The fiery water of the Phlegethon may have healed her and given her strength, but it didn’t do anything for her hunger or thirst. The river wasn’t about making you feel good, Annabeth guessed. It just kept you going so you could experience more excruciating pain.

Her head started to droop with exhaustion. Then she heard them—female voices having some sort of argument—and she was instantly alert.

She whispered, “Percy, down!”

She pulled him behind the nearest boulder, wedging herself so close against the riverbank that her shoes almost touched the river’s fire. On the other side, in the narrow path between the river and the cliffs, voices snarled, getting louder as they approached from upstream.

Annabeth tried to steady her breathing. The voices sounded vaguely human, but that meant nothing. She assumed anything in Tartarus was their enemy. She didn’t know how the monsters could have failed to spot them already. Besides, monsters could smell demigods—especially powerful ones like Percy, son of Poseidon. Annabeth doubted that hiding behind a boulder would do any good when the monsters caught their scent.

Still, as the monsters got nearer, their voices didn’t change in tone. Their uneven footsteps—scrap, clump, scrap, clump—didn’t get any faster.

“Soon?” one of them asked in a raspy voice, as if she’d been gargling in the Phlegethon.

“Oh my gods!” said another voice. This one sounded much younger and much more human, like a teenaged mortal girl getting exasperated with her friends at the mall. For some reason, she sounded familiar to Annabeth. “You guys are totally annoying! I told you, it’s like three days from here.”

Percy gripped Annabeth’s wrist. He looked at her with alarm, as if he recognized the mall girl’s voice too.

There was a chorus of growling and grumbling. The creatures—maybe half a dozen, Annabeth guessed—had paused just on the other side of the boulder, but still they gave no indication that they’d caught the demigods’ scent. Annabeth wondered if demigods didn’t smell the same in Tartarus, or if the other scents here were so powerful, they masked a demigod’s aura.

“I wonder,” said a third voice, gravelly and ancient like the first, “if perhaps you do not know the way, young one.”

“Oh, shut your fang hole, Serephone,” said the mall girl. “When’s the last time you escaped to the mortal world? I was there a couple of years ago. I know the way! Besides, I understand what we’re facing up there. You don’t have a clue!”

“The Earth Mother did not make you boss!” shrieked a fourth voice.

More hissing, scuffling, and feral moans—like giant alley cats fighting. At last the one called Serephone yelled, “Enough!”

The scuffling died down.

“We will follow for now,” Serephone said. “But if you do not lead us well, if we find you have lied about the summons of Gaea—”

“I don’t lie!” snapped the mall girl. “Believe me, I’ve got good reason to get into this battle. I have some enemies to devour, and you’ll feast on the blood of heroes. Just leave one special morsel for me—the one named Percy Jackson.”

Annabeth fought down a snarl of her own. She forgot about her fear. She wanted to jump over the boulder and slash the monsters to dust with her knife…except she didn’t have it anymore.

“Believe me,” said the mall girl. “Gaea has called us, and we’re going to have so much fun. Before this war is over, mortals and demigods will tremble at the sound of my name—Kelli!”

Annabeth almost yelped aloud. She glanced at Percy. Even in the red light of the Phlegethon, his face seemed waxy.

Empousai, she mouthed. Vampires.

Percy nodded grimly.

She remembered Kelli. Two years ago, at Percy’s freshman orientation, he and their friend Rachel Dare had been attacked by empousai disguised as cheerleaders. One of them had been Kelli. Later, the same empousa had attacked them in Daedalus’s workshop. Annabeth had stabbed her in the back and sent her…here. To Tartarus.

The creatures shuffled off, their voices getting fainter. Annabeth crept to the edge of the boulder and risked a glimpse. Sure enough, five women staggered along on mismatched legs—mechanical bronze on the left, shaggy and cloven-hooved on the right. Their hair was made of fire, their skin as white as bone. Most of them wore tattered Ancient Greek dresses, except for the one in the lead, Kelli, who wore a burned and torn blouse with a short pleated skirt…her cheerleader’s outfit.

Annabeth gritted her teeth. She had faced a lot of bad monsters over the years, but she hated empousai more than most.

In addition to their nasty claws and fangs, they had a powerful ability to manipulate the Mist. They could change shape and charmspeak, tricking mortals into letting down their guard. Men were especially susceptible. The empousa’s favorite tactic was to make a guy fall in love with her, then drink his blood and devour his flesh. Not a great first date.

Kelli had almost killed Percy. She had manipulated Annabeth’s oldest friend, Luke, urging him to commit darker and darker deeds in the name of Kronos.

Annabeth really wished she still had her dagger.

Percy rose. “They’re heading for the Doors of Death,” he murmured. “You know what that means?”

Annabeth didn’t want to think about it, but sadly, this squad of flesh-eating horror-show women might be the closest thing to good luck they were going to get in Tartarus.

“Yeah,” she said. “We need to follow them.”

LEO SPENT THE NIGHT WRESTLING with a forty-foot-tall Athena.

Ever since they’d brought the statue aboard, Leo had been obsessed with figuring out how it worked. He was sure it had primo powers. There had to be a secret switch or a pressure plate or something.

He was supposed to be sleeping, but he just couldn’t. He spent hours crawling over the statue, which took up most of the lower deck. Athena’s feet stuck into sick bay, so you had to squeeze past her ivory toes if you wanted some Advil. Her body ran the length of the port corridor, her outstretched hand jutting into the engine room, offering the life-sized figure of Nike that stood in her palm, like, Here, have some Victory! Athena’s serene face took up most of the aft pegasus stables, which were fortunately unoccupied. If Leo were a magic horse, he wouldn’t have wanted to live in a stall with an oversized goddess of wisdom staring at him.

The statue was wedged tight in the corridor, so Leo had to climb over the top and wriggle under her limbs, searching for levers and buttons.

As usual, he found nothing.

He’d done some research on the statue. He knew it was made from a hollow wooden frame covered in ivory and gold, which explained why it was so light. It was in pretty good shape, considering it was more than two thousand years old, had been pillaged from Athens, toted to Rome, and secretly stored in a spider’s cavern for most of the past two millennia. Magic must’ve kept it intact, Leo figured, combined with really good craftsmanship.

Annabeth had said…well, he tried not to think about Annabeth. He still felt guilty about her and Percy falling into Tartarus. Leo knew it was his fault. He should have gotten everyone safely on board the Argo II before he started securing the statue. He should have realized the cavern floor was unstable.

Still, moping around wasn’t going to get Percy and Annabeth back. He had to concentrate on fixing the problems he could fix.

Anyway, Annabeth had said the statue was the key to defeating Gaea. It could heal the rift between Greek and Roman demigods. Leo figured there had to be more to it than just symbolism. Maybe Athena’s eyes shot lasers, or the snake behind her shield could spit poison. Or maybe the smaller figure of Nike came to life and busted out some ninja moves.

Leo could think of all kinds of fun things the statue might do if he had designed it, but the more he examined it, the more frustrated he got. The Athena Parthenos radiated magic. Even he could feel that. But it didn’t seem to do anything except look impressive.

The ship careened to one side, taking evasive maneuvers. Leo resisted the urge to run to the helm. Jason, Piper, and Frank were on duty with Hazel now. They could handle whatever was going on. Besides, Hazel had insisted on taking the wheel to guide them through the secret pass that the magic goddess had told her about.

Leo hoped Hazel was right about the long detour north. He didn’t trust this Hecate lady. He didn’t see why such a creepy goddess would suddenly decide to be helpful.

Of course, he didn’t trust magic in general. That’s why he was having so much trouble with the Athena Parthenos. It had no moving parts. Whatever it did, it apparently operated on pure sorcery…and Leo didn’t appreciate that. He wanted it to make sense, like a machine.

Finally he got too exhausted to think straight. He curled up with a blanket in the engine room and listened to the soothing hum of the generators. Buford the mechanical table sat in the corner on sleep mode, making little steamy snores: Shhh, pfft, shh, pfft.

Leo liked his quarters okay, but he felt safest here in the heart of the ship—in a room filled with mechanisms he knew how to control. Besides, maybe if he spent more time close to the Athena Parthenos, he would eventually soak in its secrets.

“It’s you or me, Big Lady,” he murmured as he pulled the blanket up to his chin. “You’re gonna cooperate eventually.”

He closed his eyes and slept. Unfortunately, that meant dreams.

He was running for his life through his mother’s old workshop, where she’d died in a fire when Leo was eight.

He wasn’t sure what was chasing him, but he sensed it closing fast—something large and dark and full of hate.

He stumbled into workbenches, knocked over toolboxes, and tripped on electrical cords. He spotted the exit and sprinted toward it, but a figure loomed in front of him—a woman in robes of dry swirling earth, her face covered in a veil of dust.

Where are you going, little hero? Gaea asked. Stay, and meet my favorite son.

Leo darted to the left, but the Earth Goddess’s laughter followed him.

The night your mother died, I warned you. I said the Fates would not allow me to kill you then. But now you have chosen your path. Your death is near, Leo Valdez.

He ran into a drafting table—his mother’s old workstation. The wall behind it was decorated with Leo’s crayon drawings. He sobbed in desperation and turned, but the thing pursuing him now stood in his path—a colossal being wrapped in shadows, its shape vaguely humanoid, its head almost scraping the ceiling twenty feet above.