Or Annabeth will be dead, I thought, but I didn’t say that.

“We need a car,” Thalia said.

“But what about Bessie?” I asked.

Grover stopped in his tracks. “I’ve got an idea! The Ophiotaurus can appear in different bodies of water, right?”

“Well, yeah,” I said. “I mean, he was in Long Island Sound. Then he just popped into the water at Hoover Dam. And now he’s here.”

“So maybe we could coax him back to Long Island Sound,” Grover said. “Then Chiron could help us get him to Olympus.”

“But he was following me,” I said. “If I’m not there, would he know where he’s going?”

“Moo,” Bessie said forlornly.

“I . . . I can show him,” Grover said. “I’ll go with him.”

I stared at him. Grover was no fan of the water. He’d almost drowned last summer in the Sea of Monsters, and he couldn’t swim very well with his goat hooves.

“I’m the only one who can talk to him,” Grover said. “It makes sense.”

He bent down and said something in Bessie’s ear. Bessie shivered, then made a contented, lowing sound.

“The blessing of the Wild,” Grover said. “That should help with safe passage. Percy, pray to your dad, too. See if he will grant us safe passage through the seas.”

I didn’t understand how they could possibly swim back to Long Island from California. Then again, monsters didn’t travel the same way as humans. I’d seen plenty evidence of that.

I tried to concentrate on the waves, the smell of the ocean, the sound of the tide.

“Dad,” I said. “Help us. Get the Ophiotaurus and Grover safely to camp. Protect them at sea.”

“A prayer like that needs a sacrifice,” Thalia said. “Something big.”

I thought for a second. Then I took off my coat.

“Percy,” Grover said. “Are you sure? That lion skin . . . that’s really helpful. Hercules used it!”

As soon as he said that, I realized something.

I glanced at Zoë, who was watching me carefully. I realized I did know who Zoë’s hero had been—the one who’d ruined her life, gotten her kicked out of her family, and never even mentioned how she’d helped him: Hercules, a hero I’d admired all my life.

“If I’m going to survive,” I said, “it won’t be because I’ve got a lion-skin cloak. I’m not Hercules.”

I threw the coat into the bay. It turned back into a golden lion skin, flashing in the light. Then, as it began to sink beneath the waves, it seemed to dissolve into sunlight on the water.

The sea breeze picked up.

Grover took a deep breath. “Well, no time to lose.”

He jumped in the water and immediately began to sink. Bessie glided next to him and let Grover take hold of his neck.

“Be careful,” I told them.

“We will,” Grover said. “Okay, um . . . Bessie? We’re going to Long Island. It’s east. Over that way.”

“Moooo?” Bessie said.

“Yes,” Grover answered. “Long Island. It’s this island. And . . . it’s long. Oh, let’s just start.”

“Mooo!”

Bessie lurched forward. He started to submerge and Grover said, “I can’t breathe underwater! Just thought I’d mention—” Glub!

Under they went, and I hoped my father’s protection would extend to little things, like breathing.

“Well, that is one problem addressed,” Zoë said. “But how can we get to my sisters’ garden?”

“Thalia’s right,” I said. “We need a car. But there’s nobody to help us here. Unless we, uh, borrowed one.”

I didn’t like that option. I mean, sure this was a life-or-death situation, but still, it was stealing, and it was bound to get us noticed.

“Wait,” Thalia said. She started rifling through her backpack. “There is somebody in San Francisco who can help us. I’ve got the address here somewhere.”

“Who?” I asked.

Thalia pulled out a crumpled piece of notebook paper and held it up. “Professor Chase. Annabeth’s dad.”

After hearing Annabeth gripe about her dad for two years, I was expecting him to have devil horns and fangs. I was not expecting him to be wearing an old-fashioned aviator’s cap and goggles. He looked so weird, with his eyes bugging out through the glasses, that we all took a step back on the front porch.

“Hello,” he said in a friendly voice. “Are you delivering my airplanes?”

Thalia, Zoë, and I looked at each other warily.

“Um, no, sir,” I said.

“Drat,” he said. “I need three more Sopwith Camels.”

“Right,” I said, though I had no clue what he was talking about. “We’re friends of Annabeth.”

“Annabeth?” He straightened as if I’d just given him an electric shock. “Is she all right? Has something happened?”

None of us answered, but our faces must’ve told him that something was very wrong. He took off his cap and goggles. He had sandy-colored hair like Annabeth and intense brown eyes. He was handsome, I guess, for an older guy, but it looked like he hadn’t shaved in a couple of days, and his shirt was buttoned wrong, so one side of his collar stuck up higher than the other side.

“You’d better come in,” he said.

It didn’t look like a house they’d just moved into. There were LEGO robots on the stairs and two cats sleeping on the sofa in the living room. The coffee table was stacked with magazines, and a little kid’s winter coat was spread on the floor. The whole house smelled like fresh-baked chocolate-chip cookies. There was jazz music coming from the kitchen. It seemed like a messy, happy kind of home—the kind of place that had been lived in forever.

“Dad!” a little boy screamed. “He’s taking apart my robots!”

“Bobby,” Dr. Chase called absently, “don’t take apart your brother’s robots.”

“I’m Bobby,” the little boy protested. “He’s Matthew!”

“Matthew,” Dr. Chase called, “don’t take apart your brother’s robots!”

“Okay, Dad!”

Dr. Chase turned to us. “We’ll go upstairs to my study. This way.”

“Honey?” a woman called. Annabeth’s stepmom appeared in the living room, wiping her hands on a dish towel. She was a pretty Asian woman with red highlighted hair tied in a bun.

“Who are our guests?” she asked.

“Oh,” Dr. Chase said. “This is . . .”

He stared at us blankly.

“Frederick,” she chided. “You forgot to ask them their names?”

We introduced ourselves a little uneasily, but Mrs. Chase seemed really nice. She asked if we were hungry. We admitted we were, and she told us she’d bring us some cookies and sandwiches and sodas.

“Dear,” Dr. Chase said. “They came about Annabeth.”

I half expected Mrs. Chase to turn into a raving lunatic at the mention of her stepdaughter, but she just pursed her lips and looked concerned. “All right. Go on up to the study and I’ll bring you some food.” She smiled at me. “Nice meeting you, Percy. I’ve heard a lot about you.”

Upstairs, we walked into Dr. Chase’s study and I said, “Whoa!”

The room was wall-to-wall books, but what really caught my attention were the war toys. There was a huge table with miniature tanks and soldiers fighting along a blue painted river, with hills and fake trees and stuff. Old-fashioned biplanes hung on strings from the ceiling, tilted at crazy angles like they were in the middle of a dogfight.

Dr. Chase smiled. “Yes. The Third Battle of Ypres. I’m writing a paper, you see, on the use of Sopwith Camels to strafe enemy lines. I believe they played a much greater role than they’ve been given credit for.”

He plucked a biplane from its string and swept it across the battlefield, making airplane engine noises as he knocked down little German soldiers.

“Oh, right,” I said. I knew Annabeth’s dad was a professor of military history. She’d never mentioned he played with toy soldiers.

Zoë came over and studied the battlefield. “The German lines were farther from the river.”

Dr. Chase stared at her. “How do you know that?”

“I was there,” she said matter-of-factly. “Artemis wanted to show us how horrible war was, the way mortal men fight each other. And how foolish, too. The battle was a complete waste.”