“What’s this?” He wagged it at the dwarfs, who were still teary-eyed from the smoke.

“Nothing!” Akmon said. “Just a book. It had a pretty gold cover, so we took it from him.”

“Him?” Leo asked.

Akmon and Passalos exchanged a nervous look.

“Minor god,” Passalos said. “In Venice. Really, it’s nothing.”

“Venice.” Jason frowned at Leo. “Isn’t that where we’re supposed to go next?”

“Yeah.” Leo examined the book. He couldn’t read the text, but it had lots of illustrations: scythes, different plants, a picture of the sun, a team of oxen pulling a cart. He didn’t see how any of that was important, but if the book had been stolen from a minor god in Venice—the next place Hecate had told them to visit—then this had to be what they were looking for.

“Where exactly can we find this minor god?” Leo asked.

“No!” Akmon shrieked. “You can’t take it back to him! If he finds out we stole it—”

“He’ll destroy you,” Jason guessed. “Which is what we’ll do if you don’t tell us, and we’re a lot closer.” He pressed the point of his sword against Akmon’s furry throat.

“Okay, okay!” the dwarf shrieked. “La Casa Nera! Calle Frezzeria!”

“Is that an address?” Leo asked.

The dwarfs both nodded vigorously.

“Please don’t tell him we stole it,” Passalos begged. “He isn’t nice at all!”

“Who is he?” Jason asked. “What god?”

“I—I can’t say,” Passalos stammered.

“You’d better,” Leo warned.

“No,” Passalos said miserably. “I mean, I really can’t say. I can’t pronounce it! Tr—tri—It’s too hard!”

“Truh,” Akmon said. “Tru-toh—Too many syllables!”

They both burst into tears.

Leo didn’t know if the Kerkopes were telling them the truth, but it was hard to stay mad at weeping dwarfs, no matter how annoying and badly dressed they were.

Jason lowered his sword. “What do you want to do with them, Leo? Send them to Tartarus?”

“Please, no!” Akmon wailed. “It might take us weeks to come back.”

“Assuming Gaea even lets us!” Passalos sniffled. “She controls the Doors of Death now. She’ll be very cross with us.”

Leo looked at the dwarfs. He’d fought lots of monsters before and never felt bad about dissolving them, but this was different. He had to admit he sort of admired these little guys. They played cool pranks and liked shiny things. Leo could relate. Besides, Percy and Annabeth were in Tartarus right now, hopefully still alive, trudging toward the Doors of Death. The idea of sending these twin monkey boys there to face the same nightmarish problem…well, it didn’t seem right.

He imagined Gaea laughing at his weakness—a demigod too softhearted to kill monsters. He remembered his dream about Camp Half-Blood in ruins, Greek and Roman bodies littering the fields. He remembered Octavian speaking with the Earth Goddess’s voice: The Romans move east from New York. They advance on your camp, and nothing can slow them down.

“Nothing can slow them down,” Leo mused. “I wonder…”

“What?” Jason asked.

Leo looked at the dwarfs. “I’ll make you a deal.”

Akmon’s eyes lit up. “Thirty percent?”

“We’ll leave you all your treasure,” Leo said, “except the stuff that belongs to us, and the astrolabe, and this book, which we’ll take back to the dude in Venice.”

“But he’ll destroy us!” Passalos wailed.

“We won’t say where we got it,” Leo promised. “And we won’t kill you. We’ll let you go free.”

“Uh, Leo…?” Jason asked nervously.

Akmon squealed with delight. “I knew you were as smart as Hercules! I will call you Black Bottom, the Sequel!”

“Yeah, no thanks,” Leo said. “But in return for us sparing your lives, you have to do something for us. I’m going to send you somewhere to steal from some people, harass them, make life hard for them any way you can. You have to follow my directions exactly. You have to swear on the River Styx.”

“We swear!” Passalos said. “Stealing from people is our specialty!”

“I love harassment!” Akmon agreed. “Where are we going?”

Leo grinned. “Ever heard of New York?”

PERCY HAD TAKEN HIS GIRLFRIEND on some romantic walks before. This wasn’t one of them.

They followed the River Phlegethon, stumbling over the glassy black terrain, jumping crevices, and hiding behind rocks whenever the vampire girls slowed in front of them.

It was tricky to stay far enough back to avoid getting spotted but close enough to keep Kelli and her comrades in view through the dark hazy air. The heat from the river baked Percy’s skin. Every breath was like inhaling sulfur-scented fiberglass. When they needed a drink, the best they could do was sip some refreshing liquid fire.

Yep. Percy definitely knew how to show a girl a good time.

At least Annabeth’s ankle seemed to have healed. She was hardly limping at all. Her various cuts and scrapes had faded. She’d tied her blond hair back with a strip of denim torn from her pants leg, and in the fiery light of the river, her gray eyes flickered. Despite being beat-up, sooty, and dressed like a homeless person, she looked great to Percy.

So what if they were in Tartarus? So what if they stood a slim chance of surviving? He was so glad that they were together, he had the ridiculous urge to smile.

Physically, Percy felt better too, though his clothes looked like he’d been through a hurricane of broken glass. He was thirsty, hungry, and scared out of his mind (though he wasn’t going to tell Annabeth that), but he’d shaken off the hopeless cold of the River Cocytus. And as nasty as the firewater tasted, it seemed to keep him going.

Time was impossible to judge. They trudged along, following the river as it cut through the harsh landscape. Fortunately the empousai weren’t exactly speed walkers. They shuffled on their mismatched bronze and donkey legs, hissing and fighting with each other, apparently in no hurry to reach the Doors of Death.

Once, the demons sped up in excitement and swarmed something that looked like a beached carcass on the riverbank. Percy couldn’t tell what it was—a fallen monster? An animal of some kind? The empousai attacked it with relish.

When the demons moved on, Percy and Annabeth reached the spot and found nothing left except a few splintered bones and glistening stains drying in the heat of the river. Percy had no doubt the empousai would devour demigods with the same gusto.

“Come on.” He led Annabeth gently away from the scene. “We don’t want to lose them.”

As they walked, Percy thought about the first time he’d fought the empousa Kelli at Goode High School’s freshman orientation, when he and Rachel Elizabeth Dare got trapped in the band hall. At the time, it seemed like a hopeless situation. Now, he’d give anything to have a problem that simple. At least he’d been in the mortal world then. Here, there was nowhere to run.

Wow. When he started looking back on the war with Kronos as the good old days—that was sad. He kept hoping things would get better for Annabeth and him, but their lives just got more and more dangerous, as if the Three Fates were up there spinning their futures with barbed wire instead of thread just to see how much two demigods could tolerate.

After a few more miles, the empousai disappeared over a ridge. When Percy and Annabeth caught up, they found themselves at the edge of another massive cliff. The River Phlegethon spilled over the side in jagged tiers of fiery waterfalls. The demon ladies were picking their way down the cliff, jumping from ledge to ledge like mountain goats.

Percy’s heart crept into his throat. Even if he and Annabeth reached the bottom of the cliff alive, they didn’t have much to look forward to. The landscape below them was a bleak, ash-gray plain bristling with black trees, like insect hair. The ground was pocked with blisters. Every once in a while, a bubble would swell and burst, disgorging a monster like a larva from an egg.

Suddenly Percy wasn’t hungry anymore.

All the newly formed monsters were crawling and hobbling in the same direction—toward a bank of black fog that swallowed the horizon like a storm front. The Phlegethon flowed in the same direction until about halfway across the plain, where it met another river of black water—maybe the Cocytus? The two floods combined in a steaming, boiling cataract and flowed on as one toward the black fog.

The longer Percy looked into that storm of darkness, the less he wanted to go there. It could be hiding anything—an ocean, a bottomless pit, an army of monsters. But if the Doors of Death were in that direction, it was their only chance to get home.

He peered over the edge of the cliff.

“Wish we could fly,” he muttered.

Annabeth rubbed her arms. “Remember Luke’s winged shoes? I wonder if they’re still down here somewhere.”

Percy remembered. Those shoes had been cursed to drag their wearer into Tartarus. They’d almost taken his best friend, Grover. “I’d settle for a hang glider.”

“Maybe not a good idea.” Annabeth pointed. Above them, dark winged shapes spiraled in and out of the bloodred clouds.

“Furies?” Percy wondered.

“Or some other kind of demon,” Annabeth said. “Tartarus has thousands.”

“Including the kind that eats hang gliders,” Percy guessed. “Okay, so we climb.”

He couldn’t see the empousai below them anymore. They’d disappeared behind one of the ridges, but that didn’t matter. It was clear where he and Annabeth needed to go. Like all the maggot monsters crawling over the plains of Tartarus, they should head toward the dark horizon. Percy was just brimming with enthusiasm for that.

AS THEY STARTED DOWN THE CLIFF, Percy concentrated on the challenges at hand: keeping his footing, avoiding rockslides that would alert the empousai to their presence, and of course making sure he and Annabeth didn’t plummet to their deaths.

About halfway down the precipice, Annabeth said, “Stop, okay? Just a quick break.”

Her legs wobbled so badly, Percy cursed himself for not calling a rest earlier.

They sat together on a ledge next to a roaring fiery waterfall. Percy put his arm around Annabeth, and she leaned against him, shaking from exhaustion.

He wasn’t much better. His stomach felt like it had shrunk to the size of a gumdrop. If they came across any more monster carcasses, he was afraid he might pull an empousa and try to devour it.

At least he had Annabeth. They would find a way out of Tartarus. They had to. He didn’t think much of fates and prophecies, but he did believe in one thing: Annabeth and he were supposed to be together. They hadn’t survived so much just to get killed now.

“Things could be worse,” Annabeth ventured.

“Yeah?” Percy didn’t see how, but he tried to sound upbeat.