"No parents?" the fat lady asked us.

She had beady eyes; pointy, coffee-stained teeth; a floppy denim hat, and a denim dress that bulged so much, she looked like a blue-jean blimp.

"They're below," Annabeth told her. "Scared of heights."

"Oh, the poor darlings."

The Chihuahua growled. The woman said, "Now, now, sonny. Behave." The dog had beady eyes like its owner, intelligent and vicious.

I said, "Sonny. Is that his name?"

"No," the lady told me.

She smiled, as if that cleared everything up.

At the top of the Arch, the observation deck reminded me of a tin can with carpeting. Rows of tiny windows looked out over the city on one side and the river on the other. The view was okay, but if there's anything I like less than a confined space, it's a confined space six hundred feet in the air. I was ready to go pretty quick.

Annabeth kept talking about structural supports, and how she would've made the windows bigger, and designed a see-through floor. She probably could've stayed up there for hours, but luckily for me the park ranger announced that the observation deck would be closing in a few minutes.

I steered Grover and Annabeth toward the exit, loaded them into the elevator, and I was about to get in myself when I realized there were already two other tourists inside. No room for me.

The park ranger said, "Next car, sir."

"We'll get out," Annabeth said. "We'll wait with you."

But that was going to mess everybody up and take even more time, so I said, "Naw, it's okay. I'll see you guys at the bottom."

Grover and Annabeth both looked nervous, but they let the elevator door slide shut. Their car disappeared down the ramp.

Now the only people left on the observation deck were me, a little boy with his parents, the park ranger, and the fat lady with her Chihuahua.

I smiled uneasily at the fat lady. She smiled back, her forked tongue flickering between her teeth.

Wait a minute.

Forked tongue?

Before I could decide if I'd really seen that, her Chihuahua jumped down and started yapping at me.

"Now, now, sonny," the lady said. "Does this look like a good time? We have all these nice people here."

"Doggie!" said the little boy. "Look, a doggie!"

His parents pulled him back.

The Chihuahua bared his teeth at me, foam dripping from his black lips.

"Well, son," the fat lady sighed. "If you insist."

Ice started forming in my stomach. "Urn, did you just call that Chihuahua your son?"

"Chimera, dear," the fat lady corrected. "Not a Chihuahua. It's an easy mistake to make."

She rolled up her denim sleeves, revealing that the skin of her arms was scaly and green. When she smiled, I saw that her teeth were fangs. The pupils of her eyes were sideways slits, like a reptile's.

The Chihuahua barked louder, and with each bark, it grew. First to the size of a Doberman, then to a lion. The bark became a roar.

The little boy screamed. His parents pulled him back toward the exit, straight into the park ranger, who stood, paralyzed, gaping at the monster.

The Chimera was now so tall its back rubbed against the roof. It had the head of a lion with a blood-caked mane, the body and hooves of a giant goat, and a serpent for a tail, a ten-foot-long diamondback growing right out of its shaggy behind. The rhinestone dog collar still hung around its neck, and the plate-sized dog tag was now easy to read: CHIMERA—RABID, FIRE-BREATHING, POISONOUS—IF FOUND, PLEASE CALL TARTARUS—EXT. 954.

I realized I hadn't even uncapped my sword. My hands were numb. I was ten feet away from the Chimera's bloody maw, and I knew that as soon as I moved, the creature would lunge.

The snake lady made a hissing noise that might've been laughter. "Be honored, Percy Jackson. Lord Zeus rarely allows me to test a hero with one of my brood. For I am the Mother of Monsters, the terrible Echidna!"

I stared at her. All I could think to say was: "Isn't that a kind of anteater?"

She howled, her reptilian face turning brown and green with rage. "I hate it when people say that! I hate Australia! Naming that ridiculous animal after me. For that, Percy Jackson, my son shall destroy you!"

The Chimera charged, its lion teeth gnashing. I managed to leap aside and dodge the bite.

I ended up next to the family and the park ranger, who were all screaming now, trying to pry open the emergency exit doors.

I couldn't let them get hurt. I uncapped my sword, ran to the other side of the deck, and yelled, "Hey, Chihuahua!" The Chimera turned faster than I would've thought possible.

Before I could swing my sword, it opened its mouth, emitting a stench like the world's largest barbecue pit, and shot a column of flame straight at me.

I dove through the explosion. The carpet burst into flames; the heat was so intense, it nearly seared off my eyebrows.

Where I had been standing a moment before was a ragged hole in the side of the Arch, with melted metal steaming around the edges.

Great, I thought. We just blowtorched a national monument.

Riptide was now a shining bronze blade in my hands, and as the Chimera turned, I slashed at its neck.

That was my fatal mistake. The blade sparked harmlessly off the dog collar. I tried to regain my balance, but I was so worried about defending myself against the fiery lion's mouth, I completely forgot about the serpent tail until it whipped around and sank its fangs into my calf.

My whole leg was on fire. I tried to jab Riptide into the Chimera's mouth, but the serpent tail wrapped around my ankles and pulled me off balance, and my blade flew out of my hand, spinning out of the hole in the Arch and down toward the Mississippi River.

I managed to get to my feet, but I knew I had lost. I was weaponless. I could feel deadly poison racing up to my chest. I remembered Chiron saying that Anaklusmos would always return to me, but there was no pen in my pocket. Maybe it had fallen too far away. Maybe it only returned when it was in pen form. I didn't know, and I wasn't going to live long enough to figure it out.

I backed into the hole in the wall. The Chimera advanced, growling, smoke curling from its lips. The snake lady, Echidna, cackled. "They don't make heroes like they used to, eh, son?"

The monster growled. It seemed in no hurry to finish me off now that I was beaten.

I glanced at the park ranger and the family. The little boy was hiding behind his father's legs. I had to protect these people. I couldn't just… die. I tried to think, but my whole body was on fire. My head felt dizzy. I had no sword. I was facing a massive, fire-breathing monster and its mother. And I was scared.

There was no place else to go, so I stepped to the edge of the hole. Far, far below, the river glittered.

If I died, would the monsters go away? Would they leave the humans alone?

"If you are the son of Poseidon," Echidna hissed, "you would not fear water. Jump, Percy Jackson. Show me that water will not harm you. Jump and retrieve your sword. Prove your bloodline."

Yeah, right, I thought. I'd read somewhere that jumping into water from a couple of stories up was like jumping onto solid asphalt. From here, I'd splatter on impact.

The Chimera's mouth glowed red, heating up for another blast.

"You have no faith," Echidna told me. "You do not trust the gods. I cannot blame you, little coward. Better you die now. The gods are faithless. The poison is in your heart."

She was right: I was dying. I could feel my breath slowing down. Nobody could save me, not even the gods.

I backed up and looked down at the water. I remembered the warm glow of my father's smile when I was a baby. He must have seen me. He must have visited me when I was in my cradle.

I remembered the swirling green trident that had appeared above my head the night of capture the flag, when Poseidon had claimed me as his son.