The big airliner flew through the night, and Alex Sennefer sat in the dark cabin and thought about the dead and the missing. The dead: the Death Walker he had put to rest back in New York, and the one he was almost certainly flying toward. The missing: his mom.

The plane would arrive in London early the next morning. Right now, it was somewhere over the vast, cold Atlantic Ocean. Alex drummed his fingers on his thigh, impatient, wanting to be there already, wanting to get started. He looked over at his best friend, Renata Duran. Ren was conked out in the window seat. She’d placed the cheap airline pillow against the wall and crumpled sideways into it. Her eyes were closed and her mouth was just slightly open, almost touching the little window. Alex looked through the safety glass, but all he saw was moonlight and a spiderweb of frost from the minus-eighty-degree temps outside. How can she sleep with everything that’s going on? he thought. But he knew he should try to get some rest, too.

He took one last look up the aisle toward first class, where he was pretty sure his cousin Luke was already asleep. His cousin wasn’t the type to stay up thinking. He honestly wasn’t the type to think all that much while he was awake. Technically, he was headed to London to attend an elite track-and-field camp, but Alex was pretty sure he was also going to keep an official family eye on him. What’s left of the family, he thought.

He fished his pillow off the floor, stuck it behind his head, and muscled his eyes closed. He forced himself to take slow, even breaths. In the unguarded borderland between awake and asleep, a memory of his mom slipped in. His whole class had been invited to a birthday party, which was probably the only reason he had been. This was toward the end, when he was absent from school as often as he was present. And sure enough, he was too sick to go. His mom brought home ice cream and sat next to him as he curled up on the couch. He managed only one bite, but she finished the bowl and pretended they’d “shared” it. “Thanks for the ice cream,” he’d said. “It was good.” She’d reached over and smoothed out his hair, the worry lines around her eyes bunching up as she smiled.

But sleep came and took her away from him again. In her place, a nightmare. Alex was back in the Stung Man’s underground tomb, carved out of an abandoned subway station and furnished with stolen luxuries. A large black scorpion scrabbled over the fringe of a rug, and then a shadow fell over it. Alex looked up and there he was: the Stung Man, his face bloated with ancient stings and his robes smelling faintly of decay. He raised his left arm, which ended not in a hand but a massive scorpion stinger. The barbed point was the size of a carving knife. The stinger flashed forward —

Alex woke with a start. He sat up so fast that he nearly hit his forehead on the little TV screen in the seat in front of him. So much for getting some shut-eye, he thought. He looked around. The problem was the plane, this long, dark cabin. It was too much like one of the stone sarcophagi back at the Metropolitan Museum of Art, where his mom had worked as a curator before she disappeared.

He looked at the little screen, feeling both tired and restless. TV would be a good distraction.

He glanced around to make sure no one was looking. The businessman in the aisle seat was fast asleep, chin on shirt, drool on chin. Alex reached into his collar and fished his amulet out from under his blue polo shirt. It was made of polished stone and refined copper and shaped like a sacred scarab beetle, a symbol of regeneration in ancient Egypt. It had been his mom’s, and now, it seemed, it was his.

Alex was still learning what the ancient artifact could do. He knew one thing, though. Considering it had been made in a time and place where towering stone pyramids were the height of technology, the amulet made a surprisingly good remote. He closed his hand around the stone scarab and felt the rush he did whenever he used the amulet. His pulse revved and his mind focused; he felt like a race car driver rounding a curve.

The little screen blinked to life and he selected MOVIES, not with his fingers but with his eyes, and began flipping through his choices.

“What’re you watchin’?”

Alex gasped.

“Must be a scary movie,” said Ren, poking him in the shoulder.

“You just, kind of — you shouldn’t surprise people like that,” said Alex, keeping his voice low so he wouldn’t wake the beefy businessman.

“You shouldn’t zone out playing with your toy,” said Ren.

Alex looked down at the scarab. He knew she was just joking. It wasn’t a toy: It had already saved both their lives. He slipped it back under his collar.

Ren reached up and touched the screen in front of her. The first thing that came up was the flight map. Alex saw her scan the screen and read the numbers along the side. It was a British airline, and the distances were all in kilometers.

He watched her eyes narrow, her brow crease. She got one very distinct line right between her eyebrows when she concentrated. Alex thought of it as the ON button of a brown-eyed computer.

“You’re converting kilometers to miles, aren’t you?” he said.

“Yep,” she said. “It’s easy.”

“Oh yeah?” he said. He knew her too well to believe her. Ren wasn’t the type of brainiac for whom things came easy; Ren was the type who worked problems to death. “What’s 2,389 kilometers?” he said, reading the screen.

Again, the crease. “About 1,500 miles,” she said. “Maybe a little less.”

Alex didn’t doubt her math. Her dad was one of the chief engineers at the Metropolitan Museum, and the apple hadn’t fallen far from the tree. It’s just that it was a very small apple — almost a crab apple, really. She was twelve, like him, but not quite four and a half feet tall. From her seat, she had to look not only over at Alex, but also up.

There was a rumbling next to them. The businessman was climbing to his feet, looking back over his shoulder to see if there was a line for the restrooms. Alex turned back to Ren. “Wanna watch a movie?”

But Ren’s eyes were on the businessman. “Let’s go over the plan while he’s away,” she said as soon as he headed down the aisle.

Alex rolled his eyes.

“What?” said Ren.

“Never mind,” said Alex, but then he said it anyway. “What good will going over the plan up here do? We need to get down on the ground and start looking.”

“We need to know what we’re doing before we do it!” she countered.

Alex almost rolled his eyes again. It was such a Ren thing to say. A phrase the other kids used to say popped into his mind: Plus Ten Ren. Ren the planner, Ren the extra-credit gobbler …

“So, no movie?” he said.

She shook her head again. “This is important, Alex.”

He took one last look at the screen and let out an exaggerated sigh. They’d been over all this before they left, but he knew she wouldn’t yield. “Fine,” he said.

Ren heard the sigh but ignored it. She knew Alex wasn’t much of a planner. She even sort of understood it: For most of his life, his unpredictable health had made planning a waste of time. But he was better now, and this was serious. The Lost Spells his mom had used to bring him back from the brink of death had brought others back, too: Death Walkers. And the next one, they believed, was in London.

When she thought about it, she got the same flash of fear she got before tests. A pit-of-the-stomach panic she could almost taste. It used to be: Was she ready? Had she prepared enough to keep up with her classmates? What kind of grade would she bring home to her brilliant parents? She swallowed hard, knowing how much higher the stakes were now. The new questions: Was she ready? Had she prepared enough to face the new dangers ahead of them? Would she make it home at all?

“Okay,” she said, leaning in and lowering her voice. She began with what she already knew. That always settled her down some. “The Stung Man came from the museum. Which makes sense, because where else are you going to find a mummified ancient Egyptian? And we needed your scarab amulet and the spell — the right spell — from the Book of the Dead to send him back. That came from the museum, too.”

She paused to see if Alex wanted to add anything, but all he said was, “Obviously.”

She shot him a look. His expression was flat, and he was drumming his fingers on his thigh in a way that was starting to annoy her. What part of an evil spirit clinging to the edge of the afterlife and escaping at the first opportunity is obvious? she thought. Since when?

She went on. “And things started to happen all over the world as soon as the Spells were used. So things have been happening in London for a while now.”

Alex perked up, finally met Ren’s eyes. “This one’s been awake longer,” he said.

“Yeah,” she said. “So?”

But he was thinking about it now, and all he did was repeat that one word: “Longer …”

He hadn’t even been paying attention, but he’d figured something out. Something important. Ren hated it when people did that to her. WHAT? she wanted to say, but she didn’t want to look stupid. She hated that even more. “Anyway,” she said, “the main thing is the Death Walker.”

Alex looked at her, bug-eyed. “The main thing is my mom!”

“Right,” said Ren. “But we don’t even know if she’s in London.”

“She’s there,” said Alex.

“Okay, but let’s just —”

“Right, right, right,” said Alex, not bothering to hide his impatience. “We know The Order is working with the Death Walkers. And we know The Order has my mom, so if we find them, we’ll find her.”

Ren didn’t argue. They were pretty sure the ancient death cult had kidnapped Alex’s mom when they’d stolen the Lost Spells. But pretty sure wasn’t the same as knowing — and she really wished he’d stop drumming his fingers like that.

“Anyway,” she said, glancing down at the offending digits. “The first thing we need to find out is who — or what, I guess — this Death Walker is —”

“We need to get down there and get started,” said Alex, cutting her off.

She opened her mouth to respond, but he cut her off again. “All right?” he said. “Period.”

“All right,” she said, sitting back in her seat. “But stop doing that thing with your fingers. It’s annoying.”

Both their seats were jolted as the bulky businessman thumped back down. If the conversation wasn’t over before, it was now.

Alex went back to picking his movie, and Ren stared silently out her window at the red light of dawn. She’d go over it all one more time, on her own.