They hit the ground in a confusion of arms and legs and bodies and equipment, scattering across the floor like balls tossed from a hand. Peter came to rest on his back, blinking at the distant ceiling, his mind and body roaring with adrenaline.

Where was Babcock?

“Come on!” Alicia had grabbed him by the shirt and was pulling him to his feet. Sara and Caleb were beside her; Hollis was hobbling toward them, somehow still carrying his rifle. “We have to get out of here!”

“Where did it go?”

“I don’t know! It jumped away!”

The remains of the cattle were strewn everywhere. The air stank of blood, of meat. Amy was helping Maus to her feet. The girl’s clothes were still smoking, though she seemed not to notice. A patch of her hair had been scorched away, revealing a raw pinkness of scalp.

“Help Theo,” Mausami said, as Peter crouched before her.

“Maus, you’re shot.”

Her teeth were clenched with pain. She shoved him away. “Help him.”

Peter went to where his brother was kneeling in the dirt. He seemed dazed, his expression disordered. His feet were bare, his clothing was in tatters, his arms were covered with scabs. What had they done to him?

“Theo, look at me,” Peter commanded, gripping him by the shoulders. “Are you hurt? Do you think you can walk?”

A small light seemed to go on in his brother’s eyes. Not the whole Theo, but at least a glimmer.

“Oh my God,” said Caleb, “that’s Finn.”

The boy was pointing toward a bloody shape on the floor a few meters away. Peter thought at first it was a piece of the cattle, but then the details came into focus and he understood that this lump of meat and bone was half a person, a torso and head and a single arm, which lay twisted at an odd angle over the dead man’s forehead. Below the waist there was nothing. The face, just as Caleb had said, was Finn Darrell’s.

He tightened his grip on Theo’s shoulders. Sara and Alicia were lifting Mausami to her feet. “Theo, I need you to try to walk.”

Theo blinked and licked his lips. “Is it really you, brother?”

Peter nodded.

“You… came for me.”

“Caleb,” Peter said, “help me.”

Peter pulled Theo upright and wrapped an arm around his waist, Caleb taking him from the other side.

Together, they ran.

They exited into the dark tunnel, into the fleeing crowds. People were tearing toward the exit, pushing and shoving. Up ahead, Olson was waving people through the opening, screaming at the top of his voice: “Run to the train!”

They burst from the tunnel into the yard. Everyone was making for the gate, which stood open. In the darkness and confusion a bottleneck had formed, too many people trying to shove their way through the narrow opening at once. Some were attempting to scale the fence, hurling themselves against the wires and clawing their way up. As Peter watched, a man at the top fell backward, screaming, one leg tangled in the barbs.

“Caleb!” Alicia cried. “Take Maus!”

The crowd was surging around them. Peter saw Alicia’s head bobbing above the fray, a flash of blond hair he knew to be Sara’s. The two of them were moving in the wrong direction, fighting the current of the crowd.

“Lish! Where are you going?” But his voice was overpowered by a blast of sound, a single sustained note that split the air, seeming to come not from one direction but from everywhere at once.

Michael, he thought. Michael was coming.

They were suddenly propelled forward, the energy of the panicked throng lifting them like a wave. Somehow Peter managed to keep hold of his brother. They passed through the gate and into another mob of people compressed into the gap between the two fence lines. Someone banged into him from behind and he heard the man grunt and stumble and fall beneath the feet of the crowd. Peter fought his way through, pushing, shoving, using his body like a battering ram, until, at last, they burst free of the second gate.

The tracks were dead ahead. Theo seemed to be rousing, doing more to carry his own weight as they fought their way forward. In the chaos and darkness Peter couldn’t see any of the others. He called their names but heard no answer over the yelling of the figures tearing past him. The road ascended a sandy rise and as they neared the top he saw a glow of light coming from the south. Another blast of the horn and then he saw it.

A huge silver bulk churning toward them, parting the night like a blade. A single beam of light shot from its bow, shining over the masses of figures crowding around the tracks. He saw Caleb and Mausami up ahead, racing toward the front of the train. Still holding Theo, Peter stumbled down the embankment; he heard a squeal of brakes. People were racing alongside the train, trying to grab hold. As the engine drew closer, a hatch opened in the front cab and Michael leaned out.

“We can’t stop!”

“What?”

Michael cupped his mouth. “We have to keep moving!”

The train had slowed to a crawl. Peter saw Caleb and Hollis lifting a woman into one of the three open boxcars trailing the engine; Michael was helping to pull Mausami up the ladder into the cab, Amy pushing from behind. Peter began to run with his brother, trying to match their speed with the ladder; as Amy ducked into the hatch, Theo grabbed hold and began to ascend. When he reached the top, Peter dove for the ladder and pulled himself up, his feet swinging free. Behind him he heard a sound of gunfire, shots pinging off the sides of the cars.

He slammed the door closed behind him to find himself in a cramped compartment, glowing with a hundred tiny lights. Michael was sitting at the control panel, Billie beside him. Amy had withdrawn to the floor behind Michael’s chair, her eyes wide, her knees protectively pulled to her chest. To Peter’s left, a narrow hallway led aft.

“Flyers, Peter,” Michael said, swiveling in his chair. “Where the hell did Theo come from?”

Peter’s brother was slumped on the floor of the hallway; Mausami was holding his head against her chest, her bloody leg folded under her.

Peter directed his voice to the front of the cab. “Is there a med kit in this thing?”

Billie passed him a metal box. Peter popped it open and withdrew a cloth bandage, rolling it into a compress. He tore the fabric of Mausami’s pant leg away to reveal the wound, a crater of torn skin and bloody flesh, and placed the bandage against it and told her to hold it there.

Theo lifted his face, his eyes flickering. “Am I dreaming you?”

Peter shook his head.

“Who is she? The girl. I thought… ” His voice trailed away.

For the first time it struck him: he had done it. Take care of your brother.

“There’ll be time later, okay?”

Theo managed a weak smile. “Whatever you say.”

Peter moved to the front of the cab, between the two seats. Through the slit of windshield between the plates he could see a view of desert in the beam of the headlamp and the tracks rolling under them.

“Is Babcock dead?” Billie asked.

He shook his head.

“You didn’t kill him?”

The sight of the woman filled him with a sudden anger. “Where the hell was Olson?”

Before she could answer, Michael broke in. “Wait, where are the others? Where’s Sara?”

The last Peter had seen her, she was with Alicia at the gate. “I think she must be in one of the other cars.”

Billie had opened the cabin door again, leaning out; she ducked her head back inside. “I hope everybody’s on board,” she said, “because here they come. Hit the gas, Michael.”

“My sister could still be out there!” Michael shouted. “You said no one gets left!”

Billie didn’t wait. She reached across Michael, knocking him back into his chair, and gripped a lever on the panel, pushing it forward. Peter felt the train accelerate. A digital readout on the panel sprang to life, the number swiftly rising: 30, 35, 40. Then she shoved her way past Peter into the hallway, where a ladder in the wall led to a second hatch in the ceiling. She briskly ascended, turning the wheel, directing her voice to the rear of the train. “Gus! Up top, let’s go!”