"What does the equation even mean?" asked Lily. "Or signify? Or whatever you mathy people say?"

"According to Dad's notes, Uncle Henry was lecturing about exotic matter and wormholes, and these numbers," he said, trying not to sound like his father, "are one equation for the existence of a wormhole. And not just any wormhole, a traversable wormhole, in fact."

"Traversable?" said Darrell.

"Right. Traversable, as in being able to travel through it. A wormhole you can use to travel in time. Dad writes that these kinds of formulas come from astrophysicists like Kip Thorne. Dad knows Kip Thorne. I've heard him talk to him on the phone. This," he said, tapping the antique diary, "is not Copernicus. This is Thorne."

"Could I see the diary?" Darrell said. Wade passed it back to him.

"Hans Novak says Copernicus discovered it," Becca said, sounding suddenly a bit angry. "He based it on their weird journey. So, how did he come up with it? Answer that, Wade."

"Yeah, Wade," said Lily.

"I don't know. Maybe the diary is, you know, doctored somehow. Or even . . . fake."

"Fake!" Lily snapped. "People have been-"

"I know!" he said. "People have been killed. Uncle Henry was murdered . . ."

"Excuse me," Darrell said. "My mom-Sara to the rest of you-deals with old stuff like this all the time. Just looking at the ink and the paper and the condition, I think when she's back, she'd tell us that the diary's real. Genuine, she'd call it."

"Then I can't explain it," Wade said, handing the diary back to Becca. "But if Dad copied this formula from Uncle Henry's lecture, and if Uncle Henry was killed for a diary which has the same formula in it, he must have thought it was real."

"Genuine, he'd call it," Lily said quietly.

It was hard for him to admit, but he nodded. "Maybe."

Their driver suddenly took a bizarre series of tight turns, then bounced off the highway onto local roads.

"Where are we going, anyway?" Lily asked. "Carlo told us an address, but I guess I didn't hear his voice when he was talking. Does anyone remember-"

"Five, Via Rasagnole!" everyone shouted at her.

"Oh. Right." Lily shrugged. "I leave memorizing stuff to other people. Or I used to. Without my computer I guess I have to start."

"Every once in a while," Becca said, elbowing Lily gently, who then elbowed Darrell just for fun.

All of which lightened the mood, until the Maserati squealed suddenly into a lower gear. The road ahead was blocked. Flashing lights from several police vans whirled brightly, making the night air glow like a carnival.

"Roadblock," Darrell whispered. "They're with the Order. They must be. I knew it. We're doomed."

"If they're not with the Order," said Becca, "we can at least assume that they're after the dumb kids who crossed the border illegally, are concealing a deadly weapon and-now-a priceless sixteenth-century diary. We should turn around. And I mean, like, now-"

"No, no," the driver growled. Following the gestures of a policeman dressed in riot gear and wearing a helmet, she downshifted again and pulled up to the roadblock.

"Maybe the police who arrested Dad told them about us," Darrell whispered. "We're wanted criminals. Or worse."

"What's worse than being a wanted criminal?" said Lily. "Being unwanted?"

Three policemen joined the first and surrounded the car. Their expressions were grim. They rattled off a string of words so fast that Wade wondered if even Becca could follow. The driver looked slowly at each of the children then back to the policemen.

"S, va tutto bene," she said.

Wade glanced out the side window. It was maybe ten feet to the edge of the road. There was a fence. Not too high. So, they could dash to the fence. Clamber over the top. Run across the field on the other side. Maybe there was a river. A boat. They could motor down the river. The police couldn't follow their scent. Follow their scent? Now he was thinking like Darrell. Besides, they had guns and ugly expressions, so he guessed that he and his friends would be picked off in seconds.

The driver pointed across him to the glove compartment near his knees. "Apra, per favore."

He lifted a delicate silver latch and the small door dropped open. Inside was the thick brown envelope Carlo had given the driver in the garage. I should have known. A bribe! We're giving the police a bribe. We'll be sentenced to Italian jail for a hundred years for bribing law enforcement officials.

"Open, s?" said the driver, smiling at him.

Wade opened the envelope. There was no cash. No money. There were, however, five red booklets. Before he realized what they were, the policeman on his side of the car snatched them from his hands. He ran a flashlight over each one, then in the car at their faces, matching them up.

"Passports?" Lily said. "For us? But how-"

"Shh," whispered the driver.

The policeman returned the documents to Wade. On some kind of autopilot, he reinserted them in the brown envelope and tucked it back into the glove compartment, closing it with a click. He hadn't breathed for the last two minutes. The police backed away from the Maserati, calling to their counterparts. One of the vans pulled off the road and out of the way. Shifting smoothly into gear, the driver laughed and roared on into the night.

"How did we just get past those guys?" Lily asked.

Becca translated Lily's question to the driver, who, naturally, exploded in laughter.

"I documenti per viaggio di scuola. Le fotografie sono state prese dalle telecamere nei passaggi. Siamo a Roma in un'ora!"

"School travel documents, like passports for school trips," Becca said. "Our photos are from the cameras in the passages. I knew those cameras were taking our pictures!"

"And that last part, Becca?" said Darrell.

"We'll be in Rome in an hour!"

Chapter Thirty-Seven.

Somosierra, Spain March 12th 8:09 p.m.

Sixty-eight-year-old Diego Vargas, a gray-whiskered grandfather with a comb-over he was beginning to think was no longer worth the effort, pushed the gas pedal to the floor of the school bus. The rattletrap barely seemed to notice.

Climbing the foothills of the Somosierra mountains day in and day out was getting the better of the ancient vehicle. When he calculated whether the bus was older than he was, he realized it was.

By three years.

The children Diego was hauling couldn't care less. They were screaming and shouting, tossing rolled-up paper balls over their exhausted teachers' heads. It had been a very long day, far longer than the teachers expected, but that wasn't Diego's fault. The noisy children-los nios ruidosos-were having the time of their lives, and because it was the last outing of the school term, they were going out with a bang.

Still, Diego had to admit that, running late or not, the field trip to Madrid, some sixty miles south, had been all right. In the time between ferrying the monsters from the museum to the park, he'd managed to visit his son and daughter-in-law and his grandson, Emilio. Good people, all of them. The future of Spain.

"Cut it out!" "That's mine!" "Make me!" "I'll stomp your foot!" "You're lying!"

You'd think these nios would be tired at the end of such a long day. Ha! Now that they were nearing home they grew more rambunctious than ever!

Diego-and his bus-were getting far too old for this.

He jammed the shift lever, and the bus growled into a higher gear as they reached a level stretch of road. A few minutes later, he spied the opening to the mountain tunnel.

A car idled by the side of the road, lights flashing. Its door swung open and a uniformed guard waved him down with his walkie-talkie. It was Alejo. He knew Alejo and had seen him that morning.

Diego slowed the bus to a stop. "Long day for you, too, eh? Any problems?"

The guard grinned. "No, no. Just that power is out in the tunnel. No lights. Rockslides earlier this afternoon on the other side. Repairs are nearly over now, but be careful when you come through. Workers on the road. Okay?" He waved his walkie-talkie. "I'll call Nacio, tell him to expect you. And remember, slow-slow-slow!"

Diego laughed. "S, s, Alejo. Slow is this bus's specialty! We'll be on the lookout."

As the guard barked into his walkie-talkie, Diego wrenched the bus painfully into gear again and sputtered slowly into the tunnel. Like every time before, the children erupted in screams of delight as they entered the tunnel, louder now that the only light was from the headlights.

"Hush, hush!" Diego shouted over his shoulder. Like every time before, the children paid no attention at all.

On the far side of the tunnel, the night had cooled rapidly, as it always did north of the Guadarrama Mountains. Wondering when he could go home and get out of his uniform, the tunnel guard Nacio paced back and forth, observing a handful of transportation workers shovel debris from the road. Another group was scrambling around the rocks above the tunnel entrance, securing a heavy wire net across the base of the hill. Nacio glanced at his watch.

Seven o'clock. And not a minute longer. I swear, my replacement had better be here. He paused as half the workers stowed their shovels on a truck and switched to push brooms. One of the policemen called to him.

"Where is that bus, eh?"

Nacio shrugged. It had been nearly twenty minutes since Alejo's call. "He said it was coming. Even a slow bus . . ." He drifted off. Even a slow bus-even walking-wouldn't take more than ten minutes. The tunnel was less than a mile long.

The police officer switched on his high-power flashlight. "Maybe it broke down, got stuck."

"Or attacked by werewolves!"

"Yeah. And the ghost of Napoleon," the policeman laughed. "Come on."

"After this, I go home!" Nacio grumbled. "Replacement or no."

The two men walked into the dark tunnel, their flashlights combing the two lanes ahead. The tunnel had been cut through the mountain at a slight arc, so it was impossible to see through to the other end until they got to the middle.

It wasn't a long tunnel, after all, but as they neared the turn and still saw no trace of the bus, Nacio felt his heart pound faster. What would they see? Had the bus had an accident? A breakdown? Had its headlights failed, causing it to crash in the dark? But, really, if any of those things had happened, wouldn't the driver and the children have called out? Indeed, wouldn't he and the policeman have heard their echoing voices the moment they entered the tunnel? And wouldn't one of the teachers have come through to ask for help? And if, for some reason, it was still on Alejo's side, wouldn't he simply have phoned?

The policeman slowed to match his pace. They were side by side.

The silence in the tunnel was broken only by the two sets of quiet footsteps. They were nearing the end of the turn when Nacio paused to collect himself. The policeman hung back, too. There was a quiet glance between them. They started forward again. Ten feet to the end of the turn. Five feet. Two more steps.

And there in the center of the tunnel stood the other guard, Alejo. His eyes were wide. His mouth open. His trembling hand holding a flashlight. "It's you!" he said.

"Of course it's us. Where is the bus?" asked Nacio.

Alejo's face paled. "Why didn't you call me when it came through? You're supposed to call me."

Nacio turned to the policeman, then back to Alejo. "Because it never came through. Did it turn back?"

"It went into the tunnel," said Alejo. "I told you when it did. Old man Vargas drove it into the tunnel. It didn't come out on your side?"

"Of course it didn't come out!" said the policeman gruffly. "Why do you think we're standing here?"

Nacio hushed them. "Alejo, what are you saying?"

Alejo shook his head slowly. "I'm saying that I saw the school bus enter the tunnel. If it didn't exit the tunnel, then . . ."

"Then what?" said the policeman testily.

"Then it has vanished."

Chapter Thirty-Eight.

The wispy-haired driver jammed the brake to the floor of the Maserati so suddenly that Wade's forehead nearly split open across the dashboard.

"Benvenuto!" she crowed, waving her hand at the view beyond the windshield. "Ci siamo a Roma!"

They were barely fifty yards from the Colosseum, the monstrous old four-story arena of concrete and stone looming over them. Several wide streets splayed out from it in different directions.

"Which one is Via Rasagnole?" Becca asked from the backseat.

The driver, keeping her smile, took a wad of euros from a small pocket and held it in Darrell's face. "Da Carlo," she said. Then she reached over Wade and pulled the door handle, giving him a push. "Arrivederci!"

He nearly tumbled into the street. "Wait, no-"

Summoning her entire English vocabulary for the first time on their 200-mile trek, she managed to say, "All-you-out!"

"You can't just leave us here!" Lily shouted.

"Really, what about Via Rasagnole?" Darrell said, squeezing out from behind Wade's seat. "We have to go to Five, Via Rasagnole."

"Non ho mai sentito parlare della Via Rasagnole."

Becca squirmed out. "What do you mean you never heard of it? It's Via Rasagnole! Your boss told us to go there."

"Via Rasagnole! Via Rasagnole!" the driver mimicked. "Ciao!"

Gravel sprayed them like bullets as the Maserati fishtailed away and disappeared behind the Colosseum, which, no matter how cheerily it was lit up in the golden glow of spotlights, looked to Darrell like nothing but a great big monument of death.