Dr. Chase opened his mouth in shock. “You—”

“She’s a Hunter, sir,” Thalia said. “But that’s not why we’re here. We need—”

“You saw the Sopwith Camels?” Dr. Chase said. “How many were there? What formations did they fly?”

“Sir,” Thalia broke in again. “Annabeth is in danger.”

That got his attention. He set the biplane down.

“Of course,” he said. “Tell me everything.”

It wasn’t easy, but we tried. Meanwhile, the afternoon light was fading outside. We were running out of time.

When we’d finished, Dr. Chase collapsed in his leather recliner. He laced his hands. “My poor brave Annabeth. We must hurry.”

“Sir, we need transportation to Mount Tamalpais,” Zoë said. “And we need it immediately.”

“I’ll drive you. Hmm, it would be faster to fly in my Camel, but it only seats two.”

“Whoa, you have an actual biplane?” I said.

“Down at Crissy Field,” Dr. Chase said proudly. “That’s the reason I had to move here. My sponsor is a private collector with some of the finest World War I relics in the world. He let me restore the Sopwith Camel—”

“Sir,” Thalia said. “Just a car would be great. And it might be better if we went without you. It’s too dangerous.”

Dr. Chase frowned uncomfortably. “Now wait a minute, young lady. Annabeth is my daughter. Dangerous or not, I . . . I can’t just—”

“Snacks,” Mrs. Chase announced. She pushed through the door with a tray full of peanut-butter-and-jelly sandwiches and Cokes and cookies fresh out of the oven, the chocolate chips still gooey. Thalia and I inhaled a few cookies while Zoë said, “I can drive, sir. I’m not as young as I look. I promise not to destroy your car.”

Mrs. Chase knit her eyebrows. “What’s this about?”

“Annabeth is in danger,” Dr. Chase said. “On Mount Tam. I would drive them, but . . . apparently it’s no place for mortals.”

It sounded like it was really hard for him to get that last part out.

I waited for Mrs. Chase to say no. I mean, what mortal parent would allow three underage teenagers to borrow their car? To my surprise, Mrs. Chase nodded. “Then they’d better get going.”

“Right!” Dr. Chase jumped up and started patting his pockets. “My keys . . .”

His wife sighed. “Frederick, honestly. You’d lose your head if it weren’t wrapped inside your aviator hat. The keys are hanging on the peg by the front door.”

“Right!” Dr. Chase said.

Zoë grabbed a sandwich. “Thank you both. We should go. Now.”

We hustled out the door and down the stairs, the Chases right behind us.

“Percy,” Mrs. Chase called as I was leaving, “tell Annabeth . . . Tell her she still has a home here, will you? Remind her of that.”

I took one last look at the messy living room, Annabeth’s half brothers spilling LEGOs and arguing, the smell of cookies filling the air. Not a bad place, I thought.

“I’ll tell her,” I promised.

We ran out to the yellow VW convertible parked in the driveway. The sun was going down. I figured we had less than an hour to save Annabeth.

“Can’t this thing go any faster?” Thalia demanded.

Zoë glared at her. “I cannot control traffic.”

“You both sound like my mother,” I said.

“Shut up!” they said in unison.

Zoë weaved in and out of traffic on the Golden Gate Bridge. The sun was sinking on the horizon when we finally got into Marin County and exited the highway.

The roads were insanely narrow, winding through forests and up the sides of hills and around the edges of steep ravines. Zoë didn’t slow down at all.

“Why does everything smell like cough drops?” I asked.

“Eucalyptus.” Zoë pointed to the huge trees all around us.

“The stuff koala bears eat?”

“And monsters,” she said. “They love chewing the leaves. Especially dragons.”

“Dragons chew eucalyptus leaves?”

“Believe me,” Zoë said, “if you had dragon breath, you would chew eucalyptus too.”

I didn’t question her, but I did keep my eyes peeled more closely as we drove. Ahead of us loomed Mount Tamalpais. I guess, in terms of mountains, it was a small one, but it looked plenty huge as we were driving toward it.

“So that’s the Mountain of Despair?” I asked.

“Yes,” Zoë said tightly.

“Why do they call it that?”

She was silent for almost a mile before answering. “After the war between the Titans and the gods, many of the Titans were punished and imprisoned. Kronos was sliced to pieces and thrown into Tartarus. Kronos’s right-hand man, the general of his forces, was imprisoned up there, on the summit, just beyond the Garden of the Hesperides.”

“The General,” I said. Clouds seemed to be swirling around its peak, as though the mountain was drawing them in, spinning them like a top. “What’s going on up there? A storm?”

Zoë didn’t answer. I got the feeling she knew exactly what the clouds meant, and she didn’t like it.

“We have to concentrate,” Thalia said. “The Mist is really strong here.”

“The magical kind or the natural kind?” I asked.

“Both.”

The gray clouds swirled even thicker over the mountain, and we kept driving straight toward them. We were out of the forest now, into wide open spaces of cliffs and grass and rocks and fog.

I happened to glance down at the ocean as we passed a scenic curve, and I saw something that made me jump out of my seat.

“Look!” But we turned a corner and the ocean disappeared behind the hills.

“What?” Thalia asked.

“A big white ship,” I said. “Docked near the beach. It looked like a cruise ship.”

Her eyes widened. “Luke’s ship?”

I wanted to say I wasn’t sure. It might be a coincidence. But I knew better. The Princess Andromeda, Luke’s demon cruise ship, was docked at that beach. That’s why he’d sent his ship all the way down to the Panama Canal. It was the only way to sail it from the East Coast to California.

“We will have company, then,” Zoë said grimly. “Kronos’s army.”

I was about to answer, when suddenly the hairs on the back of my neck stood up. Thalia shouted, “Stop the car. NOW!”

Zoë must’ve sensed something was wrong, because she slammed on the brakes without question. The yellow VW spun twice before coming to a stop at the edge of the cliff.

“Out!” Thalia opened the door and pushed me hard. We both rolled onto the pavement. The next second: BOOOM!

Lightning flashed, and Dr. Chase’s Volkswagen erupted like a canary-yellow grenade. I probably would’ve been killed by shrapnel except for Thalia’s shield, which appeared over me. I heard a sound like metal rain, and when I opened my eyes, we were surrounded by wreckage. Part of the VW’s fender had impaled itself in the street. The smoking hood was spinning in circles. Pieces of yellow metal were strewn across the road.

I swallowed the taste of smoke out of my mouth, and looked at Thalia. “You saved my life.”

“One shall perish by a parent’s hand,” she muttered. “Curse him. He would destroy me? Me?”

It took me a second to realize she was talking about her dad. “Oh, hey, that couldn’t have been Zeus’s lightning bolt. No way.”

“Whose, then?” Thalia demanded.

“I don’t know. Zoë said Kronos’s name. Maybe he—”

Thalia shook her head, looking angry and stunned. “No. That wasn’t it.”

“Wait,” I said. “Where’s Zoë? Zoë!”

We both got up and ran around the blasted VW. Nothing inside. Nothing either direction down the road. I looked down the cliff. No sign of her.

“Zoë!” I shouted.

Then she was standing right next to me, pulling me by my arm. “Silence, fool! Do you want to wake Ladon?”

“You mean we’re here?”

“Very close,” she said. “Follow me.”

Sheets of fog were drifting right across the road. Zoë stepped into one of them, and when the fog passed, she was no longer there. Thalia and I looked at each other.

“Concentrate on Zoë,” Thalia advised. “We are following her. Go straight into the fog and keep that in mind.”