“London cabs don’t stay empty very long,” he said matter-of-factly. “Come along, kids.”

He marched off through the wrought iron gates. For a second, Sadie and I hesitated.

“Carter, what is going on?”

I shook my head. “I’m not sure I want to know.”

“Well, stay out here in the cold if you want, but I’m not leaving without an explanation.” She turned and marched after our dad.

Looking back on it, I should’ve run. I should’ve dragged Sadie out of there and gotten as far away as possible. Instead I followed her through the gates.

Chapter 2. An Explosion for Christmas

I’D BEEN TO THE BRITISH MUSEM BEFORE. In fact I’ve been in more museums than I like to admit—it makes me sound like a total geek.

[That’s Sadie in the background, yelling that I am a total geek. Thanks, Sis.]

Anyway, the museum was closed and completely dark, but the curator and two security guards were waiting for us on the front steps.

“Dr. Kane!” The curator was a greasy little dude in a cheap suit. I’d seen mummies with more hair and better teeth. He shook my dad’s hand like he was meeting a rock star. “Your last paper on Imhotep—brilliant! I don’t know how you translated those spells!”

“Im-ho-who?” Sadie muttered to me.

“Imhotep,” I said. “High priest, architect. Some say he was a magician. Designed the first step pyramid. You know.”

“Don’t know,” Sadie said. “Don’t care. But thanks.”

Dad expressed his gratitude to the curator for hosting us on a holiday. Then he put his hand on my shoulder. “Dr. Martin, I’d like you to meet Carter and Sadie.”

“Ah! Your son, obviously, and—” The curator looked hesitantly at Sadie. “And this young lady?”

“My daughter,” Dad said.

Dr. Martin’s stare went temporarily blank. Doesn’t matter how open-minded or polite people think they are, there’s always that moment of confusion that flashes across their faces when they realize Sadie is part of our family. I hate it, but over the years I’ve come to expect it.

The curator regained his smile. “Yes, yes, of course. Right this way, Dr. Kane. We’re very honored!”

The security guards locked the doors behind us. They took our luggage, then one of them reached for Dad’s workbag.

“Ah, no,” Dad said with a tight smile. “I’ll keep this one.”

The guards stayed in the foyer as we followed the curator into the Great Court. It was ominous at night. Dim light from the glass-domed ceiling cast crosshatched shadows across the walls like a giant spiderweb. Our footsteps clicked on the white marble floor.

“So,” Dad said, “the stone.”

“Yes!” the curator said. “Though I can’t imagine what new information you could glean from it. It’s been studied to death—our most famous artifact, of course.”

“Of course,” Dad said. “But you may be surprised.”

“What’s he on about now?” Sadie whispered to me.

I didn’t answer. I had a sneaking suspicion what stone they were talking about, but I couldn’t figure out why Dad would drag us out on Christmas Eve to see it.

I wondered what he’d been about to tell us at Cleopatra’s Needle—something about our mother and the night she died. And why did he keep glancing around as if he expected those strange people we’d seen at the Needle to pop up again? We were locked in a museum surrounded by guards and high-tech security. Nobody could bother us in here—I hoped.

We turned left into the Egyptian wing. The walls were lined with massive statues of the pharaohs and gods, but my dad bypassed them all and went straight for the main attraction in the middle of the room.

“Beautiful,” my father murmured. “And it’s not a replica?”

“No, no,” the curator promised. “We don’t always keep the actual stone on display, but for you—this is quite real.”

We were staring at a slab of dark gray rock about three feet tall and two feet wide. It sat on a pedestal, encased in a glass box. The flat surface of the stone was chiseled with three distinct bands of writing. The top part was Ancient Egyptian picture writing: hieroglyphics. The middle section...I had to rack my brain to remember what my dad called it: Demotic, a kind of writing from the period when the Greeks controlled Egypt and a lot of Greek words got mixed into Egyptian. The last lines were in Greek.

“The Rosetta Stone,” I said.

“Isn’t that a computer program?” Sadie asked.

I wanted to tell her how stupid she was, but the curator cut me off with a nervous laugh. “Young lady, the Rosetta Stone was the key to deciphering hieroglyphics! It was discovered by Napoleon’s army in 1799 and—”

“Oh, right,” Sadie said. “I remember now.”

I knew she was just saying that to shut him up, but my dad wouldn’t let it go.

“Sadie,” he said, “until this stone was discovered, regular mortals...er, I mean, no one had been able to read hieroglyphics for centuries. The written language of Egypt had been completely forgotten. Then an Englishman named Thomas Young proved that the Rosetta Stone’s three languages all conveyed the same message. A Frenchman named Champollion took up the work and cracked the code of hieroglyphics.”

Sadie chewed her gum, unimpressed. “What’s it say, then?”

Dad shrugged. “Nothing important. It’s basically a thank-you letter from some priests to King Ptolemy V. When it was first carved, the stone was no big deal. But over the centuries...over the centuries it has become a powerful symbol. Perhaps the most important connection between Ancient Egypt and the modern world. I was a fool not to realize its potential sooner.”

He’d lost me, and apparently the curator too.

“Dr. Kane?” he asked. “Are you quite all right?”

Dad breathed deeply. “My apologies, Dr. Martin. I was just...thinking aloud. If I could have the glass removed? And if you could bring me the papers I asked for from your archives.”

Dr. Martin nodded. He pressed a code into a small remote control, and the front of the glass box clicked open.

“It will take a few minutes to retrieve the notes,” Dr. Martin said. “For anyone else, I would hesitate to grant unguarded access to the stone, as you’ve requested. I trust you’ll be careful.”

He glanced at us kids like we were troublemakers.

“We’ll be careful,” Dad promised.

As soon as Dr. Martin’s steps receded, Dad turned to us with a frantic look in his eyes. “Children, this is very important. You have to stay out of this room.”

He slipped his workbag off his shoulder and unzipped it just enough to pull out a bike chain and padlock. “Follow Dr. Martin. You’ll find his office at the end of the Great Court on the left. There’s only one entrance. Once he’s inside, wrap this around the door handles and lock it tight. We need to delay him.”

“You want us to lock him in?” Sadie asked, suddenly interested. “Brilliant!”

“Dad,” I said, “what’s going on?”

“We don’t have time for explanations,” he said. “This will be our only chance. They’re coming.”

“Who’s coming?” Sadie asked.

He took Sadie by the shoulders. “Sweetheart, I love you. And I’m sorry...I’m sorry for many things, but there’s no time now. If this works, I promise I’ll make everything better for all of us. Carter, you’re my brave man. You have to trust me. Remember, lock up Dr. Martin. Then stay out of this room!”

Chaining the curator’s door was easy. But as soon as we’d finished, we looked back the way we’d come and saw blue light streaming from the Egyptian gallery, as if our dad had installed a giant glowing aquarium.

Sadie locked eyes with me. “Honestly, do you have any idea what he’s up to?”

“None,” I said. “But he’s been acting strange lately. Thinking a lot about Mom. He keeps her picture...”

I didn’t want to say more. Fortunately Sadie nodded like she understood.

“What’s in his workbag?” she asked.

“I don’t know. He told me never to look.”

Sadie raised an eyebrow. “And you never did? God, that is so like you, Carter. You’re hopeless.”

I wanted to defend myself, but just then a tremor shook the floor.

Startled, Sadie grabbed my arm. “He told us to stay put. I suppose you’re going to follow that order too?”

Actually, that order was sounding pretty good to me, but Sadie sprinted down the hall, and after a moment’s hesitation, I ran after her.

When we reached the entrance of the Egyptian gallery, we stopped dead in our tracks. Our dad stood in front of the Rosetta Stone with his back to us. A blue circle glowed on the floor around him, as if someone had switched on hidden neon tubes in the floor.

My dad had thrown off his overcoat. His workbag lay open at his feet, revealing a wooden box about two feet long, painted with Egyptian images.

“What’s he holding?” Sadie whispered to me. “Is that a boomerang?”

Sure enough, when Dad raised his hand, he was brandishing a curved white stick. It did look like a boomerang. But instead of throwing the stick, he touched it to the Rosetta Stone. Sadie caught her breath. Dad was writing on the stone. Wherever the boomerang made contact, glowing blue lines appeared on the granite. Hieroglyphs.

It made no sense. How could he write glowing words with a stick? But the image was bright and clear: ram’s horns above a box and an X.

“Open,” Sadie murmured. I stared at her, because it sounded like she had just translated the word, but that was impossible. I’d been hanging around Dad for years, and even I could read only a few hieroglyphs. They are seriously hard to learn.

Dad raised his arms. He chanted: “Wo-seer, i-ei.” And two more hieroglyphic symbols burned blue against the surface of the Rosetta Stone.

As stunned as I was, I recognized the first symbol. It was the name of the Egyptian god of the dead.

“Wo-seer,” I whispered. I’d never heard it pronounced that way, but I knew what it meant. “Osiris.”

“Osiris, come,” Sadie said, as if in a trance. Then her eyes widened. “No!” she shouted. “Dad, no!”

Our father turned in surprise. He started to say, “Children—” but it was too late. The ground rumbled. The blue light turned to searing white, and the Rosetta Stone exploded.

When I regained consciousness, the first thing I heard was laughter—horrible, gleeful laughter mixed with the blare of the museum’s security alarms.

I felt like I’d just been run over by a tractor. I sat up, dazed, and spit a piece of Rosetta Stone out of my mouth. The gallery was in ruins. Waves of fire rippled in pools along the floor. Giant statues had toppled. Sarcophagi had been knocked off their pedestals. Pieces of the Rosetta Stone had exploded outward with such force that they’d embedded themselves in the columns, the walls, the other exhibits.