She snuggled against him. Her hair smelled of smoke, and if he closed his eyes, he could almost imagine they were at the campfire at Camp Half-Blood.

“We could’ve fallen into the River Lethe,” she said. “Lost all our memories.”

Percy’s skin crawled just thinking about it. He’d had enough trouble with amnesia for one lifetime. Only last month, Hera had erased his memories to put him among the Roman demigods. Percy had stumbled into Camp Jupiter with no idea who he was or where he came from. And a few years before that, he’d fought a Titan on the banks of the Lethe, near Hades’s palace. He’d blasted the Titan with water from that river and completely wiped his memory clean. “Yeah, the Lethe,” he muttered. “Not my favorite.”

“What was the Titan’s name?” Annabeth asked.

“Uh…Iapetus. He said it meant the Impaler or something.”

“No, the name you gave him after he lost his memory. Steve?”

“Bob,” Percy said.

Annabeth managed a weak laugh. “Bob the Titan.”

Percy’s lips were so parched, it hurt to smile. He wondered what had happened to Iapetus after they’d left him in Hades’s palace…if he was still content being Bob, friendly, happy, and clueless. Percy hoped so, but the Underworld seemed to bring out the worst in everyone—monsters, heroes, and gods.

He gazed across the ashen plains. The other Titans were supposed to be here in Tartarus—maybe bound in chains, or roaming aimlessly, or hiding in some of those dark crevices. Percy and his allies had destroyed the worst Titan, Kronos, but even his remains might be down here somewhere—a billion angry Titan particles floating through the blood-colored clouds or lurking in that dark fog.

Percy decided not to think about that. He kissed Annabeth’s forehead. “We should keep moving. You want some more fire to drink?”

“Ugh. I’ll pass.”

They struggled to their feet. The rest of the cliff looked impossible to descend—nothing more than a crosshatching of tiny ledges—but they kept climbing down.

Percy’s body went on autopilot. His fingers cramped. He felt blisters popping up on his ankles. He got shaky from hunger.

He wondered if they would die of starvation, or if the firewater would keep them going. He remembered the punishment of Tantalus, who’d been permanently stuck in a pool of water under a fruit tree but couldn’t reach either food or drink.

Jeez, Percy hadn’t thought about Tantalus in years. That stupid guy had been paroled briefly to serve as director at Camp Half-Blood. Probably he was back in the Fields of Punishment. Percy had never felt sorry for the jerk before, but now he was starting to sympathize. He could imagine what it would be like, getting hungrier and hungrier for eternity but never being able to eat.

Keep climbing, he told himself.

Cheeseburgers, his stomach replied.

Shut up, he thought.

With fries, his stomach complained.

A billion years later, with a dozen new blisters on his feet, Percy reached the bottom. He helped Annabeth down, and they collapsed on the ground.

Ahead of them stretched miles of wasteland, bubbling with monstrous larvae and big insect-hair trees. To their right, the Phlegethon split into branches that etched the plain, widening into a delta of smoke and fire. To the north, along the main route of the river, the ground was riddled with cave entrances. Here and there, spires of rock jutted up like exclamation points.

Under Percy’s hand, the soil felt alarmingly warm and smooth. He tried to grab a handful, then realized that under a thin layer of dirt and debris, the ground was a single vast membrane…like skin.

He almost threw up, but forced himself not to. There was nothing in his stomach but fire.

He didn’t mention it to Annabeth, but he started to feel like something was watching them—something vast and malevolent. He couldn’t zero in on it, because the presence was all around them. Watching was the wrong word, too. That implied eyes, and this thing was simply aware of them. The ridges above them now looked less like steps and more like rows of massive teeth. The spires of rock looked like broken ribs. And if the ground was skin…

Percy forced those thoughts aside. This place was just freaking him out. That was all.

Annabeth stood, wiping soot from her face. She gazed toward the darkness on the horizon. “We’re going to be completely exposed, crossing this plain.”

About a hundred yards ahead of them, a blister burst on the ground. A monster clawed its way out…a glistening telkhine with slick fur, a seal-like body, and stunted human limbs. It managed to crawl a few yards before something shot out of the nearest cave, so fast that Percy could only register a dark green reptilian head. The monster snatched the squealing telkhine in its jaws and dragged it into the darkness.

Reborn in Tartarus for two seconds, only to be eaten. Percy wondered if that telkhine would pop up some other place in Tartarus, and how long it would take to re-form.

He swallowed down the sour taste of firewater. “Oh, yeah. This’ll be fun.”

Annabeth helped him to his feet. He took one last look at the cliffs, but there was no going back. He would’ve given a thousand golden drachmas to have Frank Zhang with them right now—good old Frank, who always seemed to show up when needed and could turn into an eagle or a dragon to fly them across this stupid wasteland.

They started walking, trying to avoid the cave entrances, sticking close to the bank of the river.

They were just skirting one of the spires when a glint of movement caught Percy’s eye—something darting between the rocks to their right.

A monster following them? Or maybe it was just some random baddie, heading for the Doors of Death.

Suddenly he remembered why they’d started following this route, and he froze in his tracks.

“The empousai.” He grabbed Annabeth’s arm. “Where are they?”

Annabeth scanned a three-sixty, her gray eyes bright with alarm.

Maybe the demon ladies had been snapped up by that reptile in the cave. If the empousai were still ahead of them, they should’ve been visible somewhere on the plains.

Unless they were hiding…

Too late, Percy drew his sword.

The empousai emerged from the rocks all around them—five of them forming a ring. A perfect trap.

Kelli limped forward on her mismatched legs. Her fiery hair burned across her shoulders like a miniature Phlegethon waterfall. Her tattered cheerleader outfit was splattered with rusty-brown stains, and Percy was pretty sure they weren’t ketchup. She fixed him with her glowing red eyes and bared her fangs.

“Percy Jackson,” she cooed. “How awesome! I don’t even have to return to the mortal world to destroy you!”

PERCY RECALLED HOW DANGEROUS Kelli had been the last time they’d fought in the Labyrinth. Despite those mismatched legs, she could move fast when she wanted to. She’d dodged his sword strikes and would have eaten his face if Annabeth hadn’t stabbed her from behind.

Now she had four friends with her.

“And your friend Annabeth is with you!” Kelli hissed with laughter. “Oh, yeah, I totally remember her.”

Kelli touched her own sternum, where the tip of the knife had exited when Annabeth stabbed her in the back. “What’s the matter, daughter of Athena? Don’t have your weapon? Bummer. I’d use it to kill you.”

Percy tried to think. He and Annabeth stood shoulder to shoulder as they had many times before, ready to fight. But neither of them was in good shape for battle. Annabeth was empty-handed. They were hopelessly outnumbered. There was nowhere to run. No help coming.

Briefly Percy considered calling for Mrs. O’Leary, his hellhound friend who could shadow-travel. Even if she heard him, could she make it into Tartarus? This was where monsters went when they died. Calling her here might kill her, or turn her back to her natural state as a fierce monster. No…he couldn’t do that to his dog.

So, no help. Fighting was a long shot.

That left Annabeth’s favorite tactics: trickery, talk, delay.

“So…” he started, “I guess you’re wondering what we’re doing in Tartarus.”

Kelli snickered. “Not really. I just want to kill you.”

That would’ve been it, but Annabeth chimed in.

“Too bad,” she said. “Because you have no idea what’s going on in the mortal world.”

The other empousai circled, watching Kelli for a cue to attack; but the ex-cheerleader only snarled, crouching out of reach of Percy’s sword.

“We know enough,” Kelli said. “Gaea has spoken.”

“You’re heading toward a major defeat.” Annabeth sounded so confident, even Percy was impressed. She glanced at the other empousai, one by one, then pointed accusingly at Kelli. “This one claims she’s leading you to a victory. She’s lying. The last time she was in the mortal world, Kelli was in charge of keeping my friend Luke Castellan faithful to Kronos. In the end, Luke rejected him. He gave his life to expel Kronos. The Titans lost because Kelli failed. Now Kelli wants to lead you to another disaster.”

The other empousai muttered and shifted uneasily.

“Enough!” Kelli’s fingernails grew into long black talons. She glared at Annabeth as if imagining her sliced into small pieces.

Percy was pretty sure Kelli had had a thing for Luke Castellan. Luke had that effect on girls—even donkey-legged vampires—and Percy wasn’t sure bringing up his name was such a good idea.

“The girl lies,” Kelli said. “So the Titans lost. Fine! That was part of the plan to wake Gaea! Now the Earth Mother and her giants will destroy the mortal world, and we will totally feast on demigods!”

The other vampires gnashed their teeth in a frenzy of excitement. Percy had been in the middle of a school of sharks when the water was full of blood. That wasn’t nearly as scary as empousai ready to feed.

He prepared to attack, but how many could he dispatch before they overwhelmed him? It wouldn’t be enough.

“The demigods have united!” Annabeth yelled. “You’d better think twice before you attack us. Romans and Greeks will fight you together. You don’t stand a chance!”

The empousai backed up nervously, hissing, “Romani.”

Percy guessed they’d had experience with the Twelfth Legion before, and it hadn’t worked out well for them.

“Yeah, you bet Romani.” Percy bared his forearm and showed them the brand he’d gotten at Camp Jupiter—the SPQR mark, with the trident of Neptune. “You mix Greek and Roman, and you know what you get? You get BAM!”

He stomped his foot, and the empousai scrambled back. One fell off the boulder where she’d been perched.

That made Percy feel good, but they recovered quickly and closed in again.

“Bold talk,” Kelli said, “for two demigods lost in Tartarus. Lower your sword, Percy Jackson, and I’ll kill you quickly. Believe me, there are worse ways to die down here.”

“Wait!” Annabeth tried again. “Aren’t empousai the servants of Hecate?”

Kelli curled her lip. “So?”

“So Hecate is on our side now,” Annabeth said. “She has a cabin at Camp Half-Blood. Some of her demigod children are my friends. If you fight us, she’ll be angry.”