"It's unusual equipment, captain."

Black's lips became a thin line again. Frustration and anger flickered in his eyes. "Very well," he said, "but if I see anything I consider dangerous you're all gone. Even you, sir."

The last was aimed right at Mike. He nodded.

"I'll also be taking that Glock," added Black. He held out his hand. "I'd prefer it if we're the only ones armed in there."

"We're all on the same team," said Sasha.

"Yes, ma'am. And part of a good team is knowing who should be on first base and who should be in left field."

"I hate baseball," she muttered.

Black let out a short chuckle, but his eyes didn't leave Mike's, and his hand didn't move.

Mike reached back, pulled Arthur's pistol out, and handed it to the captain. Black handed it off to Jim Duncan without looking. Duncan inspected the weapon and it vanished into an oversized pocket on his thigh. He gave his former teacher a polite nod.

Mike gestured them down the hall.

Two Marines led the way, Duncan and a man named Chavez. Two more followed behind them, and then Black, Mike, and the rest of the Door team. Weaver and the other Marine carrying explosives, a sergeant named Dylan, were next.

They moved to the big door. Duncan tried the handle, glanced at the reader, and then back to Mike. "Locked."

Mike slid between the bulk of bodies and held his card out at arm's length by the reader. "Things in here might look a little odd," he told them. "Try not to be freaked out by any of it."

There were a few snickers and grim smiles.

"If there are any enemy combatants in here, please understand they are strong and fast. They may be wearing masks to hide their faces. They're also fond of sneak attacks, so watch everywhere."

A shift rippled through the hallway. The smiles faded and the Marines changed from a small crowd of young men and women to over a dozen hardened professionals. Weapons rose a few inches. Their breathing settled.

Mike swiped his card. The door thumped open, and the Marines poured through onto the main floor. Their boots were surprisingly soft on the concrete.

He went to follow them and a hand settled on his shoulder. "Give them a minute, sir," Black said.

Mike counted seconds. The team had been on the main floor for eleven of them when he heard a metallic bang, like a minor car crash. There was a flurry of activity, and he picked out four distinct voices. One of them was swearing in Spanish.

"Clear," yelled Duncan, but there was a note in his voice.

"Staff sergeant?" called Black. He'd heard it, too.

"We're clear, sir," said Duncan, "it's just...they were right."

Black looked at Mike.

They walked out onto the main floor.

Three identical tool chests stood a few yards from the door. The sides were swollen and pushed outward. One of the chests had strings of ones and zeroes on the labels instead of letters. A drawer in another had burst open, and small fuses poured out of it in a blue and green waterfall.

Duncan walked toward them and pointed at the chest with the binary labels. "This is gonna sound crazy," he told them, "but I'm pretty sure that one wasn't here when we walked in."

The color scheme was reversed on a fourth chest-black trim on brushed-silver metal. As they walked past it, the chest shuddered, and another dent appeared with a bang. The sound echoed in the big room. Olaf and Jamie yelped and stepped back.

"Did that a minute ago, too," said one of the Marines, a squat, muscle-bound man named Costello. He carried a larger rifle than the rest. Rather than the standard magazine, it had a camouflage bag fastened in front of the trigger.

"f.u.c.k me," muttered Sasha, glaring at the tool chest.

"Just like Jiffy Pop," Mike said.

"Yeah, well, let's not be near it when it bursts."

Jamie's gaze ran down the side of the chest. "Do they still make that stuff?"

"What? Jiffy Pop?"

"Yeah?"

"I used to see it all the time back in Maine," said Staff Sgt. Duncan.

Sasha snorted.

They made their way around the cl.u.s.ter of tool chests. They all flinched when the silver chest dented outward again. This time the shape was long and wide, the blurred outline of a crescent wrench.

The rings stood tall in the middle of the room. The St. Elmo's fire spiraled along one ring, leaped to the other, and raced back. The air around them shimmered like hot pavement. They were a point of clarity in the middle of a huge double exposure.

The shimmer stretched out from wall to wall and up to the ceiling. The view of Site B spilled out beyond the rings, a crystal clear mirage hanging in the air, just like the view of the dead world had appeared on the security footage. Seven or eight feet out, the image blurred into a shimmering view of the main floor.

"Well," said Olaf, "this is new."

"Is this some kind of illusion?" asked Black.

"The instability's spreading out," Mike said. "The fold's getting bigger."

On the other side of the rings, Mike could see the safety light as it washed over Site B again and again. He watched four pa.s.ses. On the third one, the light turned amber, then back to red for the fourth.

Hundreds of bright green roaches scurried back and forth across the floor. They traced paths around the workstations and chairs. They ran alongside the cables and hoses that were still stretched across the floor. They retreated from the booted feet, then rushed out onto the floor again.

One of the roaches raced up to them and stopped seven inches from Mike's toe. Its antennae swayed back and forth in the air. Then it raced past him and vanished beneath one of the black tool chests.

"I think he likes you," Jamie said.

They made their way toward the rings. The roaches cleared out of their way, dashing aside as each foot came down. The flatscreen Mike had broken on the creature's head was still on the floor in pieces. It was also on the workstation. One of the chairs lay on its side, while its twin stood next to it. Their bases were tangled together like grasping fingers.

Five of the Marines took up positions around the rings. They kept a healthy distance. Their eyes went back and forth across the glistening air.

"S'like one of those invisibility cloaks I was telling you about," Costello said to one of the other Marines.

"It's called optical camouflage," said Mike.

"And, no," Olaf added, "it isn't."

"Some kind of hologram thing," said Weaver. Her statement leaned toward a question. "Like a...a big projection screen or something."

"It's a doorway," said Duncan. "Like a wormhole."

Mike felt a quick swell of pride for his former student. "Don't step through the fold," he said out loud. "Stay on this side of it."

Weaver and Dylan slowed their movement up the ramp. "What happens if we go through?" asked one of the Marines near the nitrogen tanks. Her tag said her name was Sann.

"You could end up dead," Mike told her. "Or lost."

"Can't get lost walking a couple of yards," muttered Costello.

"It's a lot more than a couple of yards." Mike turned his gaze to Black. "Can you destroy it?"

Black glanced at Weaver and Dylan. The edges of their mouths twitched as they bit back confident smiles. They slid the bags from their shoulders. "Fast or quiet?" Dylan asked.

Mike looked at the bags. "There's a quiet option?"

Weaver shrugged. "Relatively speaking, sir."

"Fast," he said. "The sooner this is done the better."

She nodded once and looked around the main floor. "Do we care about anything else here?"

Mike glanced back at the others. Jamie looked over toward the room that held her homemade supercomputer. Olaf stared at the rings. His shoulders sagged, just a little.

Then he met Mike's eyes and shook his head.

"No," Mike told Weaver. "You can bring the whole place down if it means being sure."

"Shouldn't need that, sir." She looked over her shoulder and found Sasha. "You're the engineer? What's under this?" She rapped one of the plastic carapaces with her knuckles. "Can we take these off?"

FORTY-NINE.

It took the Marines three minutes to accept the bolts holding the carapace sections couldn't be removed. A pile of over a dozen bra.s.s nuts sat on the pathway as a small monument to their efforts. Then Dylan had produced a small hatchet from his pack and removed several sections the direct way. It still took him four tries as he found another layer of carapace beneath each one he hacked away.

The charges were bundles of six dark green packets, bound together with loops of duct tape. They were long and rectangular and made Mike think of Jenga bricks, for some reason. The ants a.s.sembled a full label for him to read from the fragments he glimpsed. Each packet was a pound and a half, each full bundle was nine. There was a block of black plastic attached to each bundle. The detonator.

Sasha and Olaf had them place all the charges on the first ring. They used the locking points to direct the demolitions experts. Thirteen, fourteen, and fifteen had two charges each. The Marines were fast. They'd bent the charges around the carapace sections like clay and used duct tape to bind them in place, ripping off long straps of it and wrapping it around the ring. The first group had been placed in minutes.

Weaver produced a spare C4 packet and slit it open with a knife. She plucked out lumps of the white putty inside and packed it into the gaps around the charges. Dylan reached over and broke off a third of the stick and wadded it into a ball with one hand. Both of them made sure to keep their fingers clear of the threshold.

The other Marines circled the room. Two stood by the big door and two more watched the back door through the shimmering image of Site B. Four of them stood near the workstations, keeping guard as the explosives were set. Black stood between them. His face was calm, but Mike watched his eyes scan back and forth across the rings.

The others did sweep after sweep, checking everywhere. Their expressions ran from bored to confused to nervous. Several of them shot looks at the rings. All of them now held their weapons ready.

The roaches scurried between their feet. Costello tried to stomp on a few, but most of them dodged his boots with lazy circles. Even the few he connected with skittered away, still alive.

Jamie stood at the workstation, making final checks. She pursed her lips and shook her head. All the readings were stubborn to the end.

"How are you detonating them?" Mike asked.

"Remote timer," said Dylan. "We cobbled it together to meet the specs your boss gave us."

"Cobbled," echoed Weaver with a smirk.

Dylan pulled something from his vest that looked like a pistol with no actual gun barrel. "Arm it, click it, and wave goodbye to it," he said.

"How long's the timer?"

"Five and a half minutes."

"Five and a half?" echoed Jamie, looking up from her monitor. "That's kind of random."

"We usually detonate manually, ma'am," Dylan said. "Like I said, we had to throw these together kind of quick with what we had."

Weaver shuffled to the other side of the pathway. She peeled off a length of tape and fastened another charge over point three. She tore a second strip free to secure it.

The light on her face changed. The room brightened. Her eyes shifted to the left. Toward the Door. Half the Marines paused to look.

"Ahhh, f.u.c.k me," said Sasha up on the pathway. "Do you guys see that?"

The other Site B, the other version of the other building, was gone. Through the rings was a vast expanse of gray sand, lit by a twilight sun. It stretched out for over two miles, dropped away into a canyon, and then continued on the other side. The dry scent of dust and sand drifted through the rings.

"I do," Mike said. He saw Olaf and Weaver nod in his peripheral vision.

"Mother of f.u.c.king G.o.d," said Black. The view spread out wall to wall, revealing the other world to the Marines. Whispers and mutters worked their way across the main floor.

Mike saw a few withered bushes and patches of brittle gra.s.s. Nothing moved. He could see for miles, and nothing moved anywhere.

He picked out rough lines across the landscape where the sand had piled up and covered things. The ants carried out the last view through this side of the door, and pattern recognition kicked in. The layout of Site B appeared in his mind, superimposed over the desert. He made out a few buildings in the distance as well. They'd all been crushed into concrete powder and dust.

As he stared, though, one bush shifted. Not an actual movement, but a change in perspective, even though he hadn't moved or even blinked. One moment the bush was a few hundred yards from the Door, the next it was twenty-eight feet, by his estimate. Then he blinked and it retreated.

His mind replayed Arthur folding a piece of paper.

On the other side of the Door, distance seemed to be a relative term.

Dylan slammed the next charge against the ring. The tape spun around it much faster this time. The sound of tape ripping off the roll was fast and steady.