"Beat it, kid!" one of them muttered.

I moved away. They smelled pretty bad, but just regular old bad. Nothing unusual.

There was a lady with a bunch of plastic flamingos sticking out of a shopping cart. She glared at me like I was going to steal her birds.

At the end of the pier, a guy who looked about a million years old was passed out in a patch of sunlight. He wore pajamas and a fuzzy bathrobe that probably used to be white. He was fat, with a white beard that had turned yellow, kind of like Santa Claus, if Santa had been rolled out of bed and dragged through a landfill.

And his smell?

As I got closer, I froze. He smelled bad, all right—but ocean bad. Like hot seaweed and dead fish and brine. If the ocean had an ugly side… this guy was it.

I tried not to gag as I sat down near him like I was tired. Santa opened one eye suspiciously. I could feel him staring at me, but I didn't look. I muttered something about stupid school and stupid parents, figuring that might sound reasonable.

Santa Claus went back to sleep.

I tensed. I knew this was going to look strange. I didn't know how the other homeless people would react. But I jumped Santa Claus.

"Ahhhhhl" he screamed. I meant to grab him, but he seemed to grab me instead. It was as if he'd never been asleep at all. He certainly didn't act like a weak old man. He had a grip like steel. "Help me!" he screamed as he squeezed me to death.

"That's a crime!" one of the other homeless guys yelled. "Kid rolling an old man like that!"

I rolled, all right—straight down the pier until my head slammed into a post. I was dazed for a second, and Nereus's grip slackened. He was making a break for it. Before he could, I regained my senses and tackled him from behind.

"I don't have any money!" He tried to get up and run, but I locked my arms around his chest. His rotten fish smell was awful, but I held on.

"I don't want money," I said as he fought. "I'm a half-blood! I want information. "

That just made him struggle harder. "Heroes! Why do you always pick on me?"

"Because you know everything!"

He growled and tried to shake me off his back. It was like holding on to a roller coaster. He thrashed around, making it impossible for me to keep on my feet, but I gritted my teeth and squeezed tighter. We staggered toward the edge of the pier and I got an idea.

"Oh, no!" I said. "Not the water!"

The plan worked. Immediately, Nereus yelled in triumph and jumped off the edge. Together, we plunged into San Francisco Bay.

He must've been surprised when I tightened my grip, the ocean filling me with extra strength. But Nereus had a few tricks left, too. He changed shape until I was holding a sleek black seal.

I've heard people make jokes about trying to hold a greased pig, but I'm telling you, holding on to a seal in the water is harder. Nereus plunged straight down, wriggling and thrashing and spiraling through the dark water. If I hadn't been Poseidon's son, there's no way I could've stayed with him.

Nereus spun and expanded, turning into a killer whale, but I grabbed his dorsal fin as he burst out of the water.

A whole bunch of tourists went, "Whoa!"

I managed to wave at the crowd. Yeah, we do this every day here in San Francisco.

Nereus plunged into the water and turned into a slimy eel. I started to tie him into a knot until he realized what was going on and changed back to human form. "Why won't you drown?" he wailed, pummelmg me with his fists.

"I'm Poseidon's son," I said.

"Curse that upstart! I was here first!"

Finally he collapsed on the edge of the boat dock. Above us was one of those tourist piers lined with shops, like a mall on water. Nereus was heaving and gasping. I was feeling great. I could've gone on all day, but I didn't tell him that. I wanted him to feel like he'd put up a good fight.

My friends ran down the steps from the pier.

"You got him!" Zoe said.

"You don't have to sound so amazed," I said.

Nereus moaned. "Oh, wonderful. An audience for my humiliation! The normal deal, I suppose? You'll let me go if I answer your question?"

"I've got more than one question," I said.

"Only one question per capture! That's the rule."

I looked at my friends.

This wasn't good. I needed to find Artemis, and I needed to figure out what the doomsday creature was. I also needed to know if Annabeth was still alive, and how to rescue her. How could I ask that all in one question?

A voice inside me was screaming Ask about Annabeth! That's what I cared about most.

But then I imagined what Annabeth might say. She would never forgive me if I saved her and didn't save Olympus. Zoe would want me to ask about Artemis, but Chiron had told us the monster was even more important.

I sighed. "All right, Nereus. Tell me where to find this terrible monster that could bring an end to the gods. The one Artemis was hunting."

The Old Man of the Sea smiled, showing off his mossy green teeth.

"Oh, that's too easy," he said evilly. "He's right there."

Nereus pointed to the water at my feet.

"Where?" I said.

"The deal is complete!" Nereus gloated. With a pop, he turned into a goldfish and did a backflip into the sea.

"You tricked me!" I yelled.

"Wait." Thalia's eyes widened. "What is that?"

"MOOOOOOOO!"

I looked down, and there was my friend the cow serpent, swimming next to the dock. She nudged my shoe and gave me the sad brown eyes.

"Ah, Bessie," I said. "Not now."

"Mooo!"

Grover gasped. "He says his name isn't Bessie."

"You can understand her… er, him?"

Grover nodded. "It's a very old form of animal speech. But he says his name is the Ophiotaurus."

"The Ophi-what?"

"It means serpent bull in Greek," Thalia said. "But what's it doing here?"

"Moooooooo!"

"He says Percy is his protector," Grover announced.

"And he's running from the bad people. He says they are close."

I was wondering how you got all that out of a single moooooo.

"Wait," Zoe said, looking at me. "You know this cow?"

I was feeling impatient, but I told them the story.

Thalia shook her head in disbelief. "And you just forgot to mention this before?"

"Well… yeah." It seemed silly, now that she said it, but things had been happening so fast. Bessie, the Ophiotaurus, seemed like a minor detail.

"I am a fool," Zoe said suddenly. "I know this story!"

"What story?"

"From the War of the Titans," she said. "My… my father told me this tale, thousands of years ago. This is the beast we are looking for."

"Bessie?" I looked down at the bull serpent. "But… he's too cute. He couldn't destroy the world."

"That is how we were wrong," Zoe said. "We've been anticipating a huge dangerous monster, but the Ophiotaurus does not bring down the gods that way. He must be sacrificed."

"MMMM," Bessie lowed.

"I don't think he likes the S-word," Grover said.

I patted Bessie on the head, trying to calm him down. He let me scratch his ear, but he was trembling.

"How could anyone hurt him?" I said. "He's harmless."

Zoe nodded. "But there is power in killing innocence.

Terrible power. The Fates ordained a prophecy eons ago, when this creature was born. They said that whoever killed the Ophiotaurus and sacrificed its entrails to fire would have the power to destroy the gods."

"MMMMMM!"

"Um," Grover said. "Maybe we could avoid talking about entrails, too."

Thalia stared at the cow serpent with wonder. "The power to destroy the gods… how? I mean, what would happen?"

"No one knows," Zoe said. "The first time, during the Titan war, the Ophiotaurus was in fact slain by a giant ally of the Titans, but thy father, Zeus, sent an eagle to snatch the entrails away before they could be tossed into the fire. It was a close call. Now, after three thousand years, the Ophiotaurus is reborn."