He shook his head sadly. He typed, I saw nothing about the bracelet. I’m sorry. I know a little about Amaltheia the goat, but I doubt it will help. The goat nursed Zeus when he was a baby. Later, Zeus slew her and used her skin to make his shield—the aegis.

I scratched my chin. I was pretty sure that was the story I’d been trying to remember earlier about the goat’s hide. It seemed important, though I couldn’t figure out why. “So Zeus killed his own mama goat. Typical god thing to do. Thalia, you know anything about the shield?”

She nodded, clearly relieved to change the subject. “Athena put the head of Medusa on the front of it and had the whole thing covered in Celestial bronze. She and Zeus took turns using it in battle. It would frighten away their enemies.”

I didn’t see how the information could help. Obviously, the goat Amaltheia had come back to life. That happened a lot with mythological monsters—they eventually re-formed from the pit of Tartarus. But why had Amaltheia led us here?

A bad thought occurred to me. If I’d been skinned by Zeus, I definitely wouldn’t be interested in helping him anymore. In fact, I might have a vendetta against Zeus’s children. Maybe that’s why Amaltheia had brought us to the mansion.

Hal Green held out his hands to me. His grim expression told me it was my turn for a fortune-telling.

A wave of dread washed over me. After hearing Thalia’s future, I didn’t want to know mine. What if she survived, and I didn’t? What if we both survived, but Thalia sacrificed herself to save me somewhere down the line, like Hal had mentioned? I couldn’t bear that.

“Don’t, Luke,” Thalia said bitterly. “The gods were right. Hal’s prophecies don’t help anybody.”

The old man blinked his watery eyes. His hands were so frail, it was hard to believe he carried the blood of an immortal god. He had told us his curse would end today, one way or another. He’d foreseen Thalia surviving. If he saw anything in my future that would help, I had to try.

I gave him my hands.

Hal took a deep breath and closed his eyes. His snakeskin jacket glistened as if it were trying to shed. I forced myself to stay calm.

I could feel Hal’s pulse in my fingers—one, two, three.

His eyes flew open. He yanked his hands away and stared at me in terror.

“Okay,” I said. My tongue felt like sandpaper. “I’m guessing you didn’t see anything good.”

Hal turned to his computer. He stared at the screen so long I thought he’d gone into a trance.

Finally he typed, Fire. I saw fire.

Thalia frowned. “Fire? You mean today? Is that going to help us?”

Hal looked up miserably. He nodded.

“There’s more,” I pressed. “What scared you so badly?”

He avoided my eyes. Reluctantly he typed, Hard to be sure. Luke, I also saw a sacrifice in your future. A choice. But also a betrayal.

I waited. Hal didn’t elaborate.

“A betrayal,” Thalia said. Her tone was dangerous. “You mean someone betrays Luke? Because Luke would never betray anyone.”

Hal typed, His path is hard to see. But if he survives today, he will betray—

Thalia grabbed the keyboard. “Enough! You lure demigods here, then you take away their hope with your horrible predictions? No wonder the others gave up—just like you gave up. You’re pathetic!”

Anger kindled in Hal’s eyes. I didn’t think the old man had it in him, but he rose to his feet. For a moment, I thought he might lunge at Thalia.

“Go ahead,” Thalia growled. “Take a swing, old man. You have any fire left?”

“Stop it!” I ordered. Hal Green immediately backed down. I could swear the old man was terrified of me now, but I didn’t want to know what he saw in his visions. Whatever nightmares were in my future, I had to survive today first.

“Fire,” I said. “You mentioned fire.”

He nodded, then spread his hands to indicate he had no further details.

An idea buzzed in the back of my head. Fire. Greek weapons. Some of the supplies we had in this apartment…the list I’d put into the search engine, hoping for a magic formula.

“What is it?” Thalia asked. “I know that look. You’re on to something.”

“Let me see the keyboard.” I sat at the computer and did a new Web search.

An article popped up immediately.

Thalia peered over my shoulder. “Luke, that would be perfect! But I thought that stuff was just a legend.”

“I don’t know,” I admitted. “If it’s real, how do we make it? There’s no recipe here.”

Hal rapped his knuckles on the desk to get our attention. His face was animated. He pointed at his bookshelves.

“Ancient history books,” Thalia said. “Hal’s right. A lot of those are really old. They probably have information that wouldn’t be on the Internet.”

All three of us ran to the shelves. We started pulling out books. Soon Hal’s library looked like it had been hit by a hurricane, but the old man didn’t seem to care. He tossed titles and flipped through pages as fast as we did. In fact, without him, we never would’ve found the answer. After lots of fruitless searching, he came racing over, tapping a page in an old leather-bound book.

I scanned the list of ingredients, and my excitement built. “This is it. The recipe for Greek fire.”

How had I known to search for it? Perhaps my dad, Hermes, the jack-of-all-trades god, was guiding me, since he’s got a way with potions and alchemy. Perhaps I’d seen the recipe somewhere before, and searching the apartment had triggered that memory.

Everything we needed was in this room. I’d seen all of the ingredients when we’d gone through the supplies from defeated demigods: pitch from the old torches, a bottle of godly nectar, alcohol from Hal’s first-aid kit…

Actually, I shouldn’t write down the whole recipe, even in this diary. If someone came across it and learned the secret of Greek fire…well, I don’t want to be responsible for burning down the mortal world.

I read to the end of the list. There was only one thing missing.

“A catalyst.” I looked at Thalia. “We need lightning.”

Her eyes widened. “Luke, I can’t. Last time—”

Hal dragged us to the computer and typed, You can summon lightning????

“Sometimes,” Thalia admitted. “It’s a Zeus thing. But I can’t do it indoors. And even if we were outside, I’d have trouble controlling the strike. Last time, I almost killed Luke.”

The hairs on my neck stood up as I remembered that accident.

“It’ll be fine.” I tried to sound confident. “I’ll prepare the mixture. When it’s ready, there’s an outlet under the computer. You can call down a lightning strike on the house and blast it through the electrical wiring.”

“And set the house on fire,” Thalia added.

Hal typed, You’ll do that anyway if you succeed. You do understand how dangerous Greek fire is?

I swallowed. “Yeah. It’s magical fire. Whatever it touches, it burns. You can’t put it out with water, or a fire extinguisher, or anything else. But if we can make enough for some kind of bomb and throw it at the leucrotae—”

“They’ll burn.” Thalia glanced at the old man. “Please tell me the monsters aren’t immune to fire.”

Hal knit his eyebrows. I don’t think so, he typed. But Greek fire will turn this room into an inferno. It will spread through the entire house in a matter of seconds.

I looked at the empty enclosure. According to Hal’s clock, we had roughly an hour before sunset. When those bars rose and the leucrotae attacked, we might have a chance—if we could surprise the monsters with an explosion, and if we could somehow get around them and reach the escape panel at the back of the cage without getting eaten or burned alive. Too many ifs.

My mind ran through a dozen different strategies, but I kept coming back to what Hal had said about sacrifice. I couldn’t escape the feeling there was no way all three of us could get out alive.

“Let’s make the Greek fire,” I said. “Then we’ll figure out the rest.”

Thalia and Hal helped me gather the things we needed. We started Hal’s stovetop and did some extremely dangerous cooking. Time passed too quickly. Outside in the hallway, the leucrotae growled and clacked their jaws.

The drapes on the window blocked out all sunlight, but the clock told us we were almost out of time.

My face beaded with sweat as I mixed the ingredients. Every time I blinked, I remembered Hal’s words on that computer screen, as if they’d been burned onto the back of my eyes: A sacrifice in your future. A choice. But also a betrayal.

What did he mean? I was sure he hadn’t told me everything. But one thing was clear: My future terrified him.

I tried to focus on my work. I didn’t really know what I was doing, but I had no choice. Maybe Hermes was watching out for me, lending me some of his alchemy know-how. Or maybe I just got lucky. Finally I had a pot full of goopy black gunk, which I poured into an old glass jelly jar. I sealed the lid.

“There.” I handed the jar to Thalia. “Can you zap it? The glass should keep it from exploding until we break the jar.”

Thalia didn’t look thrilled. “I’ll try. I’ll have to expose some wiring in the wall. And to summon the lightning, that’ll take a few minutes of concentration. You guys should probably step back, in case…you know, I explode or something.”

She grabbed a screwdriver from Hal’s kitchen drawer, crawled under the computer desk, and stared tinkering with the outlet.

Hal picked up his green leather diary. He gestured for me to follow him. We walked to the closet doorway, where Hal took a pen from his jacket and flipped through the book. I saw pages and pages of neat, cramped handwriting. Finally Hal found an empty page and scribbled something.

He handed the book to me.

The note read, Luke, I want you to take this diary. It has my predictions, my notes about the future, my thoughts about where I went wrong. I think it might help you.

I shook my head. “Hal, this is yours. Keep it.”

He took back the book and wrote, You have an important future. Your choices will change the world. You can learn from my mistakes, continue the diary. It might help you with your decisions.

“What decisions?” I asked. “What did you see that scared you so badly?”

His pen hovered over the page for a long time. I think I finally understand why I was cursed, he wrote. Apollo was right. Sometimes the future really is better left a mystery.

“Hal, your father was a jerk. You didn’t deserve—”

Hal tapped the page insistently. He scribbled, Just promise me you’ll keep up with the diary. If I’d started recording my thoughts earlier in my life, I might have avoided some stupid mistakes. And one more thing—

He set the pen in his diary and unclipped the Celestial bronze dagger from his belt. He offered it to me.

“I can’t,” I told him. “I mean, I appreciate it, but I’m more of a sword guy. And besides, you’re coming with us. You’ll need that weapon.”