You're going to ask how the "invincible" thing worked: if I magically dodged every weapon, or if the weapons hit me and just didn't harm me. Honestly, I don't remember. All I knew was that I wasn't going to let these monsters invade my hometown.

I sliced through armor like it was made of paper. Snake women exploded. Hellhounds melted to shadow. I slashed and stabbed and whirled, and I might have even laughed once or twice—a crazy laugh that scared me as much as it did my enemies. I was aware of the Apollo campers behind me shooting arrows, disrupting every attempt by the enemy to rally. Finally, the monsters turned and fled—about twenty left alive out of two hundred.

I followed with the Apollo campers at my heels.

"Yes!" yelled Michael Yew. "That's what I'm talking about!"

We drove them back toward the Brooklyn side of the bridge. The sky was growing pale m the east. I could see the toll stations ahead.

"Percy!" Annabeth yelled. "You've already routed them. Pull back! We're overextended!"

Some part of me knew she was right, but I was doing so well, I wanted to destroy every last monster.

Then I saw the crowd at the base of the bridge. The retreating monsters were running straight toward their reinforcements. It was a small group, maybe thirty or forty demigods in battle armor, mounted on skeletal horses. One of them held a purple banner with the black scythe design.

The lead horseman trotted forward. He took off his helm, and I recognized Kronos himself, his eyes like molten gold.

Annabeth and the Apollo campers faltered. The monsters we'd been pursuing reached the Titan's line and were absorbed into the new force. Kronos gazed in our direction. He was a quarter mile away, but I swear I could see him smile.

"Now," I said, "we pull back."

The Titan lord's men drew their swords and charged. The hooves of their skeletal horses thundered against the pavement. Our archers shot a volley, bringing down several of the enemy, but they just kept riding.

"Retreat!" I told my friends. "I'll hold them.'"

In a matter of seconds they were on me.

Michael and his archers tried to retreat, but Annabeth stayed right beside me, fighting with her knife and mirrored shield as we slowly backed up the bridge.

Kronos's cavalry swirled around us, slashing and yelling insults. The Titan himself advanced leisurely, like he had all the time in the world. Being the lord of time, I guess he did.

I tried to wound his men, not kill. That slowed me down, but these weren't monsters. They were demigods who'd fallen under Kronos's spell. I couldn't see faces under l heir battle helmets, but some of them had probably been my friends. I slashed the legs off their horses and made the skeletal mounts disintegrate. After the first few demigods took a spill, the rest figured out they'd better dismount and fight me on foot.

Annabeth and I stayed shoulder to shoulder, facing opposite directions. A dark shape passed over me, and I dared to glance up. Blackjack and Porkpie were swooping in, kicking our enemies in the helmets and flying away like very large kamikaze pigeons.

We'd almost made it to the middle of the bridge when something strange happened. I felt a chill down my spine—like that old saying about someone walking on your grave. Behind me, Annabeth cried out in pain.

"Annabeth!" I turned in time to see her fall, clutching her arm. A demigod with a bloody knife stood over her.

In a flash I understood what had happened. He'd been trying to stab me. Judging from the position of his blade, he would've taken me—maybe by sheer luck—in the small of my back, my only weak point.

Annabeth had intercepted the knife with her own body.

But why? She didn't know about my weak spot. No one did.

I locked eyes with the enemy demigod. He wore an eye patch under his war helm: Ethan Nakamura, the son of Nemesis. Somehow he'd survived the explosion on the Princess Andromeda. I slammed him in the face with my sword hilt so hard I dented his helm.

"Get back!" I slashed the air in a wide arc, driving the rest of the demigods away from Annabeth. "No one touches her!"

"Interesting," Kronos said.

He towered above me on his skeletal horse, his scythe in one hand. He studied the scene with narrowed eyes as if he could sense that I'd just come close to death, the way a wolf can smell fear.

"Bravely fought, Percy Jackson," he said. "But it's time to surrender . . . or the girl dies."

"Percy, don't," Annabeth groaned. Her shirt was soaked with blood. I had to get her out of here.

"Blackjack!" I yelled.

As fast as light, the pegasus swooped down and clamped his teeth on the straps of Annabeth's armor. They soared away over the river before the enemy could even react.

Kronos snarled. "Some day soon, I am going to make pegasus soup. But in the meantime . . ." He dismounted, his scythe glistening in the dawn light. "I'll settle for another dead demigod."

I met his first strike with Riptide. The impact shook the entire bridge, but I held my ground. Kronos's smile wavered.

With a yell, I kicked his legs out from under him. His scythe skittered across the pavement. I stabbed downward, but he rolled aside and regained his footing. His scythe flew back to his hands.

"So . . ." He studied me, looking mildly annoyed. "You had the courage to visit the Styx. I had to pressure Luke in many ways to convince him. If only you had supplied my host body instead . . . But no matter. I am still more powerful. I am a TITAN."

He struck the bridge with the butt of his scythe, and a wave of pure force blasted me backward. Cars went careening. Demigods—even Luke's own men—were blown off the edge of the bridge. Suspension cords whipped around, and I skidded halfway back to Manhattan.

I got unsteadily to my feet. The remaining Apollo campers had almost made it to the end of the bridge, except for Michael Yew, who was perched on one of the suspension cables a few yards away from me, His last arrow was notched in his bow.

"Michael, go!" I screamed.

"Percy, the bridge!" he called. "It's already weak!"

At first I didn't understand. Then I looked down and saw fissures in the pavement. Patches of the road were half melted from Greek fire. The bridge had taken a beating from Kronos's blast and the exploding arrows.

"Break it!" Michael yelled. "Use your powers!"

It was a desperate thought—no way it would work— but I stabbed Riptide into the bridge. The magic blade sank to its hilt m asphalt. Salt water shot from the crack like I'd hit a geyser. I pulled out my blade and the fissure grew. The bridge shook and began to crumble. Chunks the size of houses fell into the East River. Kronos's demigods cried out in alarm and scrambled backward. Some were knocked off their feet. Within a few seconds, a fifty-foot chasm opened in the Williamsburg Bridge between Kronos and me.

The vibrations died. Kronos's men crept to the edge and looked at the hundred-and-thirty-foot drop into the river.

I didn't feel safe, though. The suspension cables were still attached. The men could get across that way if they were brave enough. Or maybe Kronos had a magic way to span the gap.

The Titan lord studied the problem. He looked behind him at the rising sun, then smiled across the chasm. He raised his scythe in a mock salute. "Until this evening, Jackson."

He mounted his horse, whirled around, and galloped back to Brooklyn, followed by his warriors.

I turned to thank Michael Yew, but the words died in my throat. Twenty feet away, a bow lay in the street. Its owner was nowhere to be seen.

"No!" I searched the wreckage on my side of the bridge. I stared down at the river. Nothing.

I yelled in anger and frustration. The sound carried forever in the morning stillness. I was about to whistle for Blackjack to help me search, when my mom's phone rang. The LCD display said I had a call from Finklestein & Associates—probably a demigod calling on a borrowed phone.