Prometheus paled. "I misspoke, my lord. Your orders will be carried out." He turned to the armies and shouted, "PREPARE FOR BATTLE!"

The troops began to stir.

From somewhere behind the UN compound, an angry roar shook the city—the sound of a drakon waking. The noise was so horrible it woke me, and I realized I could still hear it from a mile away.

Grover stood next to me, looking nervous. "What was that?"

"They're coming," I told him. "And we're in trouble."

The Hephaestus cabin was out of Greek fire. The Apollo cabin and the Hunters were scrounging for arrows. Most of us had already ingested so much ambrosia and nectar we didn't dare take any more.

We had sixteen campers, fifteen Hunters, and half a dozen satyrs left in fighting shape. The rest had taken refuge on Olympus. The Party Ponies tried to form ranks, but they staggered and giggled and they all smelled like root beer. The Texans were head-butting the Coloradoans. The Missouri branch was arguing with Illinois. The chances were pretty good the whole army would end up fighting each other rather than the enemy.

Chiron trotted up with Rachel on his back. I felt a twinge of annoyance because Chiron rarely gave anyone a ride, and never a mortal.

"Your friend here has some useful insights, Percy," he said.

Rachel blushed. "Just some things I saw in my head."

"A drakon," Chiron said. "A Lydian drakon, to be exact. The oldest and most dangerous kind."

I stared at her. "How did you know that?"

"I'm not sure," Rachel admitted. "But this drakon has a particular fate. It will be killed by a child of Ares."

Annabeth crossed her arms. "How can you possibly know that?"

"I just saw it. I can't explain."

"Well, let's hope you're wrong," I said. "Because we're a little short on children of Ares. . . ." A horrible thought occurred to me, and I cursed in Ancient Greek.

"What?" Annabeth asked.

"The spy," I told her. "Kronos said, We know they cannot beat this drakon. The spy has been keeping him updated. Kronos knows the Ares cabin isn't with us. He intentionally picked a monster we can't kill."

Thalia scowled. "If I ever catch your spy, he's going to be very sorry. Maybe we could send another messenger to camp—"

"I've already done it," Chiron said. "Blackjack is on his way. But if Silena wasn't able to convince Clarisse, I doubt Blackjack will be able—"

A roar shook the ground. It sounded very close.

"Rachel," I said, "get inside the building."

"I want to stay."

A shadow blotted out the sun. Across the street, the drakon slithered down the side of a skyscraper. It roared, and a thousand windows shattered.

"On second thought," Rachel said in a small voice, "I'll be inside."

Let me explain: there are dragons, and then there are drakons.

Drakons are several millennia older than dragons, and much larger. They look like giant serpents. Most don't have wings. Most don't breathe fire (though some do). All are poisonous. All are immensely strong, with scales harder than titanium. Their eyes can paralyze you; not the turn-you~to-stone Medusa-type paralysis, but the oh~my~gods-that~big~snake~is~going~to~eat~me type of paralysis, which is just as bad.

We have drakon-fighting classes at camp, but there is no way to prepare yourself for a two-hundred-foot-long serpent as thick as a school bus slithering down the side of a building, its yellow eyes like searchlights and its mouth full of razor-sharp teeth big enough to chew elephants.

It almost made me long for the flying pig.

Meanwhile, the enemy army advanced down Fifth Avenue. We'd done our best to push cars out of the way to keep the mortals safe, but that just made it easier for our enemies to approach. The Party Ponies swished their tails nervously. Chiron galloped up and down their ranks, shouting encouragement to stand tough and think about victory and root beer, but I figured any second they would panic and run.

"I'll take the drakon." My voice came out as a timid squeak. Then I yelled louder: "I'LL TAKE THE DRAKON! Everyone else, hold the line against the army!"

Annabeth stood next to me. She had pulled her owl helmet low over her face, but I could tell her eyes were red.

"Will you help me?" I asked.

"That's what I do," she said miserably. "I help my friends."

I felt like a complete jerk. I wanted to pull her aside and explain that I didn't mean for Rachel to be here, that it wasn't my idea, but we had no time.

"Go invisible," I said. "Look for weak links in its armor while I keep it busy. Just be careful."

I whistled. "Mrs. O'Leary, heel!"

"ROOOF!" My hellhound leaped over a line of centaurs and gave me a kiss that smelled suspiciously of pepperoni pizza.

I drew my sword and we charged the monster.

The drakon was three stories above us, slithering sideways along the building as it sized up our forces. Wherever it looked, centaurs froze in fear.

From the north, the enemy army crashed into the Party Ponies, and our lines broke. The drakon lashed out, swallowing three Californian centaurs in one gulp before I could even get close.

Mrs. O'Leary launched herself through the air—a deadly black shadow with teeth and claws. Normally, a pouncing hellhound is a terrifying sight, but next to the drakon, Mrs. O'Leary looked like a child's night-night doll.

Her claws raked harmlessly off the drakon's scales. She bit the monster's throat but couldn't make a dent. Her weight, however, was enough to knock the drakon off the side of the building. It flailed awkwardly and crashed to the sidewalk, hellhound and serpent twisting and thrashing. The drakon tried to bite Mrs. O'Leary, but she was too close to the serpent's mouth. Poison spewed everywhere, melting centaurs into dust along with quite a few monsters, but Mrs. O'Leary weaved around the serpent's head,scratching and biting.

"YAAAH!" I plunged Riptide deep into the monster's left eye. The spotlight went dark. The drakon hissed and reared back to strike, but I rolled aside.

It bit a swimming-pool-size chunk out of the pavement. It turned toward me with its good eye, and I focused on its teeth so I wouldn't get paralyzed. Mrs. O'Leary did her best to cause a distraction. She leaped onto the serpent's head and scratched and growled like a really angry black wig.

The rest of the battle wasn't going well. The centaurs had panicked under the onslaught of giants and demons. An occasional orange camp T-shirt appeared in the sea of fighting, but quickly disappeared. Arrows screamed. Fire exploded in waves across both armies, but the action was moving across the street to the entrance of the Empire State Building. We were losing ground.

Suddenly Annabeth materialized on the drakon's back. Her invisibility cap rolled off her head as she drove her bronze knife between a chink in the serpent's scales.

The drakon roared. It coiled around, knocking Annabeth off its back.

I reached her just as she hit the ground. I dragged her out of the way as the serpent rolled, crushing a lamppost right where she'd been.

"Thanks," she said.

"I told you to be careful!"

"Yeah, well, DUCK!"

It was her turn to save me. She tackled me as the monster's teeth snapped above my head. Mrs. O'Leary body-slammed the drakon's face to get its attention, and we rolled out of the way.

Meanwhile our allies had retreated to the doors of the Empire State Building. The entire enemy army was surrounding them.

We were out of options. No more help was coming. Annabeth and I would have to retreat before we were cut off from Mount Olympus.

Then I heard a rumbling in the south. It wasn't a sound you hear much in New York, but I recognized it immediately: chariot wheels.

A girl's voice yelled, "ARES!"

And a dozen war chariots charged into battle. Each flew a red banner with the symbol of the wild boar's head. Each was pulled by a team of skeletal horses with manes of fire. A total of thirty fresh warriors, armor gleaming and eyes full of hate, lowered their lances as one—making a bristling wall of death.

"The children of Ares!" Annabeth said in amazement. "How did Rachel know?"

I didn't have an answer. But leading the charge was a girl in familiar red armor, her face covered by a boar's-head helm. She held aloft a spear that crackled with electricity. Clarisse herself had come to the rescue. While half her chariots charged the monster army, Clarisse led the other six straight for the drakon.

The serpent reared back and managed to throw off Mrs. O'Leary. My poor pet hit the side of the building with a yelp. I ran to help her, but the serpent had already zeroed in on the new threat. Even with only one eye, its glare was enough to paralyze two chariot drivers. They veered into a line of cars. The other four chariots kept charging. The monster bared its fangs to strike and got a mouthful of Celestial bronze javelins.

"EEESSSSS!!!!!" it screamed, which is probably drakon for OWWWW!

"Ares, to me!" Clarisse screamed. Her voice sounded shriller than usual, but I guess that wasn't surprising given what she was fighting.

Across the street, the arrival of six chariots gave the Party Ponies new hope. They rallied at the doors of the Empire State Building, and the enemy army was momentarily thrown into confusion.

Meanwhile, Clarisse's chariots circled the drakon. Lances broke against the monster's skin. Skeletal horses breathed fire and whinnied. Two more chariots overturned, but the warriors simply leaped to their feet, drew their swords, and went to work. They hacked at chinks in the creature's scales. They dodged poison spray like they'd been training for this all their lives, which of course they had.

No one could say the Ares campers weren't brave. Clarisse was right there in front, stabbing her spear at the drakon's face, trying to put out its other eye. But as I watched, things started to go wrong. The drakon snapped up one Ares camper in a gulp. It knocked aside another and sprayed poison on a third, who retreated in a panic, his armor melting.

"We have to help," Annabeth said.

She was right. I'd just been standing there frozen in amazement. Mrs. O'Leary tried to get up but yelped again. One of her paws was bleeding.

"Stay back, girl," I told her. "You've done enough already."

Annabeth and I jumped onto the monster's back and ran toward its head, trying to draw its attention away from Clarisse.

Her cabinmates threw javelins, most of which broke, but some lodged in the monster's teeth. It snapped its jaws together until its mouth was a mess of green blood, yellow foamy poison, and splintered weapons.

"You can do it!" I screamed at Clarisse. "A child of Ares is destined to kill it!"

Through her war helmet, I could only see her eyes—but I could tell something was wrong. Her blue eyes shone with fear. Clarisse never looked like that. And she didn't have blue eyes.

"ARES!" she shouted, in that strangely shrill voice. She leveled her spear and charged the drakon.

"No," I muttered. "WAIT!"

But the monster looked down at her—almost in contempt—and spit poison directly in her face.

She screamed and fell.

"Clarisse!" Annabeth jumped off the monster's back and ran to help, while the other Ares campers tried to defend their fallen counselor. I drove Riptide between two of the creature's scales and managed to turn its attention on me.