Hermes snorted. “Of course. I checked the security cameras in the area. I talked with the wind nymphs. The thief was clearly Cacus.”

“Cacus.” I’d had years of practice looking dumb when people threw out Greek names I didn’t know. It’s a skill of mine. Annabeth keeps telling me to read a book of Greek myths, but I don’t see the need. It’s easier just to have folks explain stuff.

“Good old Cacus,” I said. “I should probably know who that is—”

“Oh, he’s a giant,” Hermes said dismissively. “A small giant, not one of the big ones.”

“A small giant.”

“Yes. Maybe ten feet tall.”

“Tiny, then,” I agreed.

“He’s a well-known thief. Stole Apollo’s cattle once.”

“I thought you stole Apollo’s cattle.”

“Well, yes. But I did it first, and with much more style. At any rate, Cacus is always stealing things from the gods. Very annoying. He used to hide out in a cave on Capitoline Hill, where Rome was founded. Nowadays, he’s in Manhattan. Underground somewhere, I’m sure.”

I took a deep breath. I saw where this was going. “Now you’re going to explain to me why you, a superpowerful god, can’t just go get your staff back yourself, and why you need me, a sixteen-year-old kid, to do it for you.”

Hermes tilted his head. “Percy, that almost sounded like sarcasm. You know very well the gods can’t go around busting heads and ripping up mortal cities looking for our lost items. If we did that, New York would be destroyed every time Aphrodite lost her hairbrush, and believe me, that happens a lot. We need heroes for that sort of errand.”

“Uh-huh. And if you went looking for the staff yourself, it might be a little embarrassing.”

Hermes pursed his lips. “All right. Yes. The other gods would certainly take notice. Me, the god of thieves, being stolen from. And my caduceus, no less, symbol of my power! I’d be ridiculed for centuries. The idea is too horrible. I need this resolved quickly and quietly before I become the laughingstock of Olympus.”

“So…you want us to find this giant, get back your caduceus, and return it to you. Quietly.”

Hermes smiled. “What a fine offer! Thank you. And I’ll need it before five o’clock this evening so I can finish my deliveries. The caduceus serves as my signature pad, my GPS, my phone, my parking permit, my iPod Shuffle—really, I can’t do a thing without it.”

“By five.” I didn’t have a watch, but I was pretty sure it was at least one o’clock already. “Can you be more specific about where Cacus is?”

Hermes shrugged. “I’m sure you can figure that out. And just a warning: Cacus breathes fire.”

“Naturally,” I said.

“And do be mindful of the caduceus. The tip can turn people to stone. I had to do that once with this horrible tattletale named Battus…but I’m sure you’ll be careful. And of course you’ll keep this as our little secret.”

He smiled winningly. Maybe I was imagining that he’d just threatened to petrify me if I told anyone about the theft.

I swallowed the sawdust taste out of my mouth. “Of course.”

“You’ll do it, then?”

An idea occurred to me. Yes—I do get ideas occasionally.

“How about we trade favors?” I suggested. “I help you with your embarrassing situation; you help me with mine.”

Hermes raised an eyebrow. “What did you have in mind?”

“You’re the god of travel, right?”

“Of course.” I told him what I wanted for my reward.

I was in better spirits when I rejoined Annabeth. I’d made arrangements to meet Hermes at Rockefeller Center no later than five, and his delivery truck had disappeared in a flash of light. Annabeth waited by our picnic site with her arms folded indignantly.

“Well?” she demanded.

“Good news.” I told her what we had to do.

She didn’t slap me, but she looked like she wanted to. “Why is tracking down a fire-breathing giant good news? And why do I want to help out Hermes?”

“He’s not so bad,” I said. “Besides, two innocent snakes are in trouble. George and Martha must be terrified—”

“Is this an elaborate joke?” she asked. “Tell me you planned this with Hermes, and we’re actually going to a surprise party for our anniversary.”

“Um…Well, no. But afterward, I promise—”

Annabeth raised her hand. “You’re cute and you’re sweet, Percy. But please—no more promises. Let’s just find this giant.”

She stowed our blanket in her backpack and put away the food. Sad…since I’d barely tasted any of the pizza. The only thing she kept out was her shield.

Like a lot of magic items, it was designed to morph into a smaller item for easy carrying. The shield shrinks to plate size, which is what we’d been using it for. Great for cheese and crackers.

Annabeth brushed off the crumbs and tossed the plate into the air. It expanded as it spun. When it landed in the grass it was a full-sized bronze shield, its highly polished surface reflecting the sky.

The shield had come in handy during our war with the Titans, but I wasn’t sure how it could help us now.

“That thing only shows aerial images, right?” I asked. “Cacus is supposed to be underground.”

Annabeth shrugged. “Worth a try. Shield, I want to see Cacus.”

Light rippled across the bronze surface.

Instead of a reflection, we were looking down at a landscape of dilapidated warehouses and crumbling roads. A rusty water tower rose above the urban blight.

Annabeth snorted. “This stupid shield has a sense of humor.”

“What do you mean?” I asked.

“That’s Secaucus, New Jersey. Read the sign on the water tower.” She rapped her knuckles on the bronze surface. “Okay, very funny, shield. Now I want to see—I mean, show me the location of the fire-breathing giant Cacus.”

The image changed.

This time I saw a familiar part of Manhattan: renovated warehouses, brick-paved streets, a glass hotel, and an elevated train track that had been turned into a park with trees and wildflowers. I remembered my mom and stepdad taking me there a few years ago when it first opened.

“That’s the High Line park,” I said. “In the Meatpacking District.”

“Yeah,” Annabeth agreed. “But where’s the giant?”

She frowned in concentration. The shield zoomed in on an intersection blocked off with orange barricades and detour signs. Construction equipment sat idle in the shadow of the High Line. Chiseled in the street was a big square hole, cordoned off with yellow police tape. Steam billowed from the pit.

I scratched my head. “Why would the police seal off a hole in the street?”

“I remember this,” Annabeth said. “It was on the news yesterday.”

“I don’t watch the news.”

“A construction worker got hurt. Some freak accident way below the surface. They were digging a new service tunnel or something, and a fire broke out.”

“A fire,” I said. “As in, maybe a fire-breathing giant?”

“That would make sense,” she agreed. “The mortals wouldn’t understand what was happening. The Mist would obscure what they really saw. They’d think the giant was just like—I don’t know—a gas explosion or something.”

“So let’s catch a cab.”

Annabeth gazed wistfully across the Great Lawn. “First sunny day in weeks, and my boyfriend wants to take me to a dangerous cave to fight a fire-breathing giant.”

“You’re awesome,” I said.

“I know,” Annabeth said. “You’d better have something good planned for dinner.”

The cab dropped us off on West 15th. The streets were bustling with a mix of sidewalk vendors, workers, shoppers, and tourists. Why a place called the Meatpacking District was suddenly a hot area to hang out, I wasn’t sure. But that’s the cool thing about New York. It’s always changing. Apparently even monsters wanted to stay here.

We made our way to the construction site. Two police officers stood at the intersection, but they didn’t pay us any attention as we turned up the sidewalk and then doubled back, ducking behind the barricades.

The hole in the street was about the size of a garage door. Pipe scaffolding hung over it with a sort of winch system, and metal climbing rungs had been fastened into the side of the pit, leading down.

“Ideas?” I asked Annabeth.

I figured I’d ask. Being the daughter of the goddess of wisdom and strategy, Annabeth likes making plans.

“We climb down,” she said. “We find the giant. We get the caduceus.”

“Wow,” I said. “Both wise and strategic.”

“Shut up.”

We climbed over the barricade, ducked under the police tape, and crept toward the hole. I kept a wary eye on the police, but they didn’t turn around. Sneaking into a dangerous steaming pit in the middle of a New York intersection proved disturbingly easy.

We descended. And descended.

The rungs seemed to go down forever. The square of daylight above us got smaller and smaller until it was the size of a postage stamp. I couldn’t hear the city traffic anymore, just the echo of trickling water. Every twenty feet or so, a dim light flickered next to the ladder, but the descent was still gloomy and creepy.

I was vaguely aware that the tunnel was opening up behind me into a much larger space, but I stayed focused on the ladder, trying not to step on Annabeth’s hands as she climbed below me. I didn’t realize we’d reached the bottom until I heard Annabeth’s feet splash.

“Holy Hephaestus,” she said. “Percy, look.”

I dropped next to her in a shallow puddle of muck. I turned and found that we were standing in a factory-sized cavern. Our tunnel emptied into it like a narrow chimney. The rock walls bristled with old cables, pipe, and lines of brickwork—maybe the foundations of old buildings. Busted water pipes, possibly old sewer lines, sent a steady drizzle of water down the walls, turning the floor muddy. I didn’t want to know what was in that water.

There wasn’t much light, but the cavern looked like a cross between a construction zone and a flea market. Scattered around the cave were crates, toolboxes, pallets of timber, and stacks of steel pipe. There was even a bulldozer half-sunken in the mud.

Even stranger: several old cars had somehow been brought from the surface, each filled with suitcases and mounds of purses. Racks of clothing had been carelessly tossed around like somebody had cleaned out a department store. Worst of all, hanging from meat hooks on a stainless steel scaffold was a row of cow carcasses—skinned, gutted, and ready for butchering. Judging from the smell and the flies, they weren’t very fresh. It was almost enough to make me turn vegetarian, except for the pesky fact that I loved cheeseburgers.

No sign of a giant. I hoped he wasn’t home. Then Annabeth pointed to the far end of the cave. “Maybe down there.”