I nodded. I’d completely forgotten my last conversation with the sun god.

“The old man of the sea,” I remembered. “I’m supposed to find him and force him to tell us what he knows. But how do I find him?”

Zoë made a face. “Old Nereus, eh?”

“You know him?” Thalia asked.

“My mother was a sea goddess. Yes, I know him. Unfortunately, he is never very hard to find. Just follow the smell.”

“What do you mean?” I asked.

“Come,” she said without enthusiasm. “I will show thee.”

I knew I was in trouble when we stopped at the Goodwill drop box. Five minutes later, Zoë had me outfitted in a ragged flannel shirt and jeans three sizes too big, bright red sneakers, and a floppy rainbow hat.

“Oh, yeah,” Grover said, trying not to bust out laughing, “you look completely inconspicuous now.”

Zoë nodded with satisfaction. “A typical male vagrant.”

“Thanks a lot,” I grumbled. “Why am I doing this again?”

“I told thee. To blend in.”

She led the way back down to the waterfront. After a long time spent searching the docks, Zoë finally stopped in her tracks. She pointed down a pier where a bunch of homeless guys were huddled together in blankets, waiting for the soup kitchen to open for lunch.

“He will be down there somewhere,” Zoë said. “He never travels very far from the water. He likes to sun himself during the day.”

“How do I know which one is him?”

“Sneak up,” she said. “Act homeless. You will know him. He will smell . . . different.”

“Great.” I didn’t want to ask for particulars. “And once I find him?”

“Grab him,” she said. “And hold on. He will try anything to get rid of thee. Whatever he does, do not let go. Force him to tell thee about the monster.”

“We’ve got your back,” Thalia said. She picked something off the back of my shirt—a big clump of fuzz that came from who-knows-where. “Eww. On second thought . . . I don’t want your back. But we’ll be rooting for you.”

Grover gave me a big thumbs-up.

I grumbled how nice it was to have super-powerful friends. Then I headed toward the dock.

I pulled my hat down and stumbled like I was about to pass out, which wasn’t hard considering how tired I was. I passed our homeless friend from the Embarcadero, who was still trying to warn the other guys about the metal angels from Mars.

He didn’t smell good, but he didn’t smell . . . different. I kept walking.

A couple of grimy dudes with plastic grocery bags for hats checked me out as I came close.

“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.

“Ahhhhh!” 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, pummeling 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!” Zoë 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. Zoë 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?”