The square corridor opened into a larger round tunnel, its ceiling lined with ducts and pipes. The walls were so heavily tagged they might have been an undiscovered Jackson Pollock masterpiece. Empty cans, dirty clothes, and mildewed sleeping bags littered the floor, filling the air with the unmistakable odor of a homeless camp: sweat, urine, and utter despair.

None of us spoke. I tried to breathe as little as possible until we emerged into an even larger tunnel, this one lined with rusty train tracks. Along the walls, pitted metal signs read HIGH VOLTAGE, NO ENTRY, and THIS WAY OUT.

Railroad gravel crunched under our feet. Rats scurried along the tracks, chittering at Grover as they passed.

“Rats,” he whispered, “are so rude.”

After a hundred yards, Piper led us into a side hallway, this one tiled in linoleum. Half-burned-out banks of fluorescents flickered overhead. In the distance, barely visible in the dim light, two figures were slumped together on the floor. I assumed they were homeless people until Meg froze. “Are those dryads?”

Grover yelped in alarm. “Agave? Money Maker?” He sprinted forward, the rest of us following at his heels.

Agave was an enormous nature spirit, worthy of her plant. Standing, she would have been at least seven feet tall, with blue-gray skin, long limbs, and serrated hair that must’ve been literally murder to shampoo. Around her neck, her wrists, and her ankles, she wore spiked bands, just in case anyone tried to intrude on her personal space. Kneeling next to her friend, Agave didn’t look too bad until she turned, revealing her burns. The left side of her face was a mass of charred tissue and glistening sap. Her left arm was nothing but a desiccated brown curl.

“Grover!” she rasped. “Help Money Maker. Please!”

He knelt next to the stricken dryad.

I’d never heard of a money maker plant before, but I could see how she got her name. Her hair was a thick cluster of plaited disks like green quarters. Her dress was made of the same stuff, so she appeared to be clad in a shower of chlorophyll coinage. Her face might have once been beautiful, but now it was shriveled like a week-old party balloon. From the knees down, her legs were gone—burned away. She tried to focus on us, but her eyes were opaque green. When she moved, jade coins dropped from her hair and dress.

“Grover’s here?” She sounded like she was breathing a mixture of cyanide gas and metal filings. “Grover…we got so close.”

The satyr’s lower lip trembled. His eyes rimmed with tears. “What happened? How—?”

“Down there,” said Agave. “Flames. She just came out of nowhere. Magic—” She began coughing up sap.

Piper peered warily down the corridor. “I’m going to scout ahead. Be right back. I do not want to be caught by surprise.”

She dashed off down the hall.

Agave tried to speak again but fell over sideways. Somehow, Meg caught her and propped her up without getting impaled. She touched the dryad’s shoulder, muttering under her breath Grow, grow, grow. Cracks began to mend in Agave’s charred face. Her breathing eased. Then Meg turned to Money Maker. She placed her hand on the dryad’s chest, then recoiled as more jade petals shook loose.

“I can’t do much for her down here,” Meg said. “They both need water and sunlight. Right now.”

“I’ll get them to the surface,” Grover said.

“I’ll help,” Meg said.

“No.”

“Grover—”

“No!” His voice cracked. “Once I’m outside, I can heal them as well as you can. This is my search party, here on my orders. It’s my responsibility to help them. Besides, your quest is down here with Apollo. You really want him going on without you?”

I thought this was an excellent point. I would need Meg’s help.

Then I noticed the way they were both looking at me, as if they doubted my abilities, my courage, my capacity to finish this quest without a twelve-year-old girl holding my hand.

They were right, of course, but that made it no less embarrassing.

I cleared my throat. “Well, I’m sure if I had to…”

Meg and Grover had already lost interest in me, as if my feelings were not their primary concern. (I know. I couldn’t believe it either.) Together they helped Agave to her feet.

“I’m fine,” Agave insisted, tottering dangerously. “I can walk. Just get Money Maker.”

Gently, Grover picked her up.

“Careful,” Meg warned. “Don’t shake her or she’ll lose all her petals.”

“Don’t shake Money Maker,” Grover said. “Got it. Good luck!”

Grover hurried into the darkness with the two dryads just as Piper returned.

“Where are they going?” she asked.

Meg explained.

Piper’s frown deepened. “I hope they get out okay. If that guard wakes up…” She let the thought expire. “Anyway, we’d better keep going. Stay alert. Heads on a swivel.”

Short of injecting myself with pure caffeine and electrifying my underwear, I wasn’t sure how I could possibly be more alert or swivel-headed, but Meg and I followed Piper down the grim fluorescent hall.

Another thirty yards, and the corridor opened into a vast space that looked like…

“Wait,” I said. “Is this an underground parking garage?”

It certainly seemed so, except for the complete absence of cars. Stretching into the darkness, the polished cement floor was painted with yellow directional arrows and rows of empty grid spaces. Lines of square pillars supported the ceiling twenty feet above. Posted on some of them were signs like: HONK. EXIT. YIELD TO LEFT.

In a car-crazy town like LA, it seemed odd that anyone would abandon a usable parking garage. Then again, I supposed street meters sounded pretty good when your other option was a creepy maze frequented by taggers, dryad search parties, and government workers.

“This is the place,” Piper said. “Where Jason and I got separated.”

The smell of sulfur was stronger here, mixed with a sweeter fragrance…like cloves and honey. It made me edgy, reminding me of something I couldn’t quite place—something dangerous. I resisted the urge to run.

Meg wrinkled her nose. “Pee-yoo.”

“Yeah,” Piper agreed. “That smell was here last time. I thought it meant…” She shook her head. “Anyway, right about here, a wall of flames came roaring out of nowhere. Jason ran right. I ran left. I’m telling you—that heat seemed malevolent. It was the most intense fire I’ve ever felt, and I’ve fought Enceladus.”

I shivered, remembering that giant’s fiery breath. We used to send him boxes of chewable antacids for Saturnalia, just to make him mad.

“And after you and Jason got separated?” I asked.

Piper moved to the nearest pillar. She ran her hand along the letters of a YIELD sign. “I tried to find him, of course. But he just disappeared. I searched for a long time. I was pretty freaked-out. I wasn’t going to lose another…”

She hesitated, but I understood. She had already suffered the loss of Leo Valdez, who until recently she had assumed dead. She wasn’t going to lose another friend.

“Anyway,” she said, “I started smelling that fragrance. That kind of clove scent?”