"Got it." Wade crouched and eased his way down one step at a time. His legs were quivering. He paused and looked up. "Dad, you're coming down with us, aren't you?"

A siren screamed on the streets outside the cemetery. Everyone froze. It got louder and louder, then its tones modulated, and it faded in the streets.

The Doppler effect, Wade thought, to steady himself. The decreasing pitch of an object retreating from you. Science. You can count on science. It's rational. Logical. There are no crypt keepers. No ghosts. Rats? Well, maybe.

"I think I'd better keep watch up here," Dr. Kaplan said. "Just in case."

"In case . . . of what?" asked Lily.

"I don't even know," he said frankly, "but I'm sure people would be angry if they saw us doing this. I'd rather they deal with me. Wade, take my notebook. Write down any words if you see any. Then let's get out of there. Go back home. Case closed."

Wade gulped in a breath of the somewhat fresher air of the tomb and continued his descent to the floor below. Lily, who had the phone again, and Becca followed him. Darrell finally put his foot onto the first step, saying, "If we find skeletons of the last kids who did this, I'm going to be very upset."

The walls on either side of the stairs were black with age and slimy with lichen.

"This is like . . . ," Lily started, then stopped when she flashed her light on the walls below. "Uh-oh . . ."

Niches cut into the walls were crammed with dozens of skulls and stacks of detached bones.

Darrell lowered his head. "I knew it. We're going to die. I'm officially upset."

"It's a catacomb," Becca whispered. "With, it looks like, hundreds of skeletons."

Wade nearly fell on an iron grate that had long ago fallen out of the wall, littering the steps with shards of cracked bone. He lifted the grate out of the way. "Are these Frieda Kupfermann's ancestors? There are so many."

"Not all of them," said Lily. She shone her light over several niches, all bearing the identical date from 1794. "Maybe there was a plague. Or a war?"

"Let's either get back up or keep going," said Darrell. "I can't stay here anymore."

Passing the bones as quickly as they could, they discovered a sunken floor with an opening in the same right-hand corner as the tomb above.

Because no one else seemed eager, Wade crawled slowly down four steps into a lower compartment, and they followed.

The floor dimensions of the subcrypt were the same as the main tomb above, but its ceiling was so low that the kids had to move forward on their hands and knees.

Underwater. That's what it feels like. Being underwater.

Darrell was snorting over and over, noisily trying to expel the musty air. Becca was quiet. Thinking, probably. She's always thinking.

"Huh," said Lily. "Look at this."

In the dim phone light, they saw walls covered with graffiti, but not the spray-painted sort you see on city streets. These were notes, numbers, initials, and pictures scratched into the stones like ancient hieroglyphs. Some were very old.

"Here are initials from 1607," whispered Becca. "People have been coming here for a long time."

"And it looks like they all died here, too," Darrell said. "Keep moving."

Secured to the front wall of the tomb was a plate made of the same mottled bronze as the tomb door above them. Wade knelt in front of it and Becca inched up beside him. "It's too small to be a burial vault," she said. "It looks more like the door of a safe."

Stamped on the plate was a small, shield-like crest with a flourish of three capital letters entwined so intricately it took them several minutes to make them out.

"G . . . A . . . C," Lily said finally.

There was also a quote inscribed above the door. It was in English.

THE FIRST WILL CIRCLE TO THE LAST.

"I'm writing it down." Wade flipped the notebook to the end. Beneath the translation of Uncle Henry's email and the words Frau Munch had written, he added these new words.

Other than the crest there were no marks anywhere on the vault except a tiny round spot about the size of a dime in one corner. Shining her cell phone light on it, Lily ran her fingers over it.

"It's not a button, is it?" Becca asked.

"I'll tell you what it looks like," said Lily. "It looks like the grill of a microphone. The kind on computers and phones. Look." She tugged out her tablet and, sure enough, there was the very same kind of circle in the corner, although the tablet's was much smaller.

"Voice recognition maybe?" said Darrell. "A security thing?"

"Kids," Dr. Kaplan called from above. "Did you find anything? What's down there? We can't linger." His words were clipped, worried.

"A safe or something," Lily said.

"Can you get it open?"

"We'll try," Wade replied.

Darrell shook his head. "Okay. So, even if this is a safe and there's no way to open it but a microphone on the door for security, what are we supposed to say into it? We have no clue."

Becca shook her head. "Except we probably do have a clue. We've gotten this far on clues Uncle Henry gave us. He supplied us with a bunch of them. All the quotes. Wade's star chart. The sundial. The name of this tomb. There have been clues every inch of the way here. Maybe there's something in what we already know."

"So for the safe to open, we say some words into the microphone?" asked Wade, reading the notebook. "Which words? What if it's keyed to a certain voice?"

"But Uncle Henry told us to come here," said Lily. "Why did he do that if we can't open it?"

Darrell made a sudden jerky movement. "Hold on." He dug his fingers into his pocket and pulled out the pitch pipe Frau Munch had shoved in his hand. "Maybe the secret thing isn't a voice at all. What if it's music? I mean, the howze kipper gave us this as part of Uncle Henry's last clue. Maybe because someone would need it to crack the safe."

"Which makes sense," said Lily. "If this safe is part of the secret, it probably wouldn't be only one person's voice, right? If something happened to that person, the safe could never be opened-"

"Someone's coming, a car," Dr. Kaplan hissed from the top of the stairs. "You need to get up here." There came the distant sound of vehicles approaching.

"Keep going," said Becca. "How many notes are there on the pitch pipe?"

"A complete octave, including sharps and flats," said Darrell.

"Play all the notes into the microphone," Becca said.

Darrell leaned close to the tiny grill on the bronze plate. With each note he played, Wade hoped the safe would pop open and they could get out of there. But nothing happened. The vault didn't budge.

"Kids, what's happening down there?"

"Do it again," said Lily. "I heard something when you played certain notes. Do it slowly."

Darrell played the notes again from lowest to highest.

A . . . click . . . B-flat . . . B . . . C . . . click . . . D-flat . . . D . . . E-flat . . . E . . . F . . . F-sharp . . . G . . . click . . . A-flat . . . A . . . click.

A tiny noise sounded behind the safe after three notes. A, C, and G.

Becca closed her eyes tight, then opened them. "That's another clue. A, C, and G are the letters on the crest. Play them in the right order. G, A, C."

Darrell played the three notes. The safe clicked three times, but did not open. Then he played the notes in every combination of the three. The safe still didn't open.

"Maybe play them all at once," said Lily. "Not separately, but altogether. They call it a chord."

"I know what a chord is," Darrell said, giving her a look. "But the three notes are all around the pitch pipe. I know I talk a lot, but I don't have three mouths-"

Lily laughed. "But we do! I mean, what if no single person can get in there, but you need several people. That's kind of a security thing, right? Three of us can play all three notes at the same time-"

"Get up here now!" hissed Dr. Kaplan. "More cars are coming. The police must know we've broken in. We're going to be arrested!"

Becca shook her head. "We only need two people. If we stop the A-flat with a finger, G and A are close enough for one person to play them at the same time. That leaves one person to play C. Who's going to do this with me?"

"I'll take G and A," Wade blurted out despite himself.

"Get up here!" Dr. Kaplan shouted. "I mean it!"

"Do it," Lily urged. "Hurry up."

Wade found himself cheek to cheek with Becca, her hair against his face, their breaths practically mingling. She nodded, and they blew out the three notes at the same time. G, A, C.

Click-click-click. Tumblers shifted behind the bronze door, there was a sudden whisper of release, and the safe in the lower chamber of the Kupfermann tomb at St. Matthew's cemetery in Berlin swung open.

"Miss Krause, the gate is locked-"

"Drive through it!" Galina shouted from the backseat. The silver SUV bounded over the sidewalk, burst through the gate, and roared down the main road of the cemetery.

It lay on a velvet cloth inside the compartment as if it had been there for centuries.

A slender dagger.

Its blade, narrowing from an inch wide at the hilt to a point as sharp as a needle, was formed of burnished iron, and its razor-like edges undulated like a silver wave.

Carved into its contoured ivory handle, twined in the same manner as the letters in the tomb's crest, were two initials.

AM.

Wade reached in and took up the dagger, and the moment he touched it his ears began to buzz and his heart pounded. "Oh man, it's heavy. And feels really old. This is so . . ."

"Kids! It sounds like a military invasion up here!" Dr. Kaplan whisper-yelled. "We-need-to-leave!"

Wade just had time to grab the velvet cloth and shut the safe door before Becca yanked him by the collar toward the stairs.

Chapter Twenty-Three.

The three SUVs swerved into the lead of a second group of vehicles racing in from another entrance.

Galina's black hair flew back into Ebner's face as she lowered the window. "Cut the lights. Stop here."

The nameless driver did as he was commanded, and Galina slid from the vehicle as silent as a snake. The other vehicles parked nearby. A large dull-gray van pulled up last.

Frail light flickered behind the open door of an old tomb with a Gothic name on it. I was right. Again. Herr Vogel was a man of humor, after all. Even in death, he revealed a joke. Kupfermann. Copper man. Copernicus.

"Galina." Ebner tilted his computer. "The recipient of Vogel's email." The screen displayed the photo of a tall man with a close-cut beard, standing in a lecture hall.

"A teacher?"

"Astronomer."

"Of course." Thrusting her hand inside her coat, Galina removed a silver pistol. "Send in the Crows."

Seven men in ski masks emerged from the back of the gray van and converged on the tomb like ghosts, slipping past the bronze door without a sound. Galina tilted her face up and scanned the open sky. It had cleared, and there were stars everywhere, so much more visible over an old graveyard than from the living streets.

Stars and the dead and the past.

Her heart pounding, Galina again saw the snowy Frombork tower in flames. And-as if the two things were connected by more than memory-the scar on her neck began to sting. It burned as it had when she received it, four years ago, a gift of three brilliant doctors in a distant Russian clinic.

Three brilliant doctors who were, alas, now dead. There had been flames in the snow there, too, a tragic fire that destroyed that clinic. Fire was an efficient way to unmake so many things.

"Miss Krause . . ."

She refocused on the heavily armed man trotting toward her.

"The tomb is empty," he said, pulling off his mask. "There is a crypt beneath the floor and a hidden safe."

"And?" she said.

"Also empty."

Galina Krause gripped the slim handle of her pistol, rage trembling through her arm, her hand and fingers. "No," she said quietly.

"Miss-"

"No. No. No!" And she fired into the trees. One, two, three, four, five times.