The foremost door on the third passenger car blew open and Captain MacGruder came shoving through it, with Inspector Galeano at his side. The captain pointed out a spot on the defensive line and told the Mexican, “There. And we’ll put your partner at the first car so we can make use of you both.”

The inspector pulled a gleaming, silver-wheeled pistol out of a carved-leather holster and let it spin as he twisted it with his wrist and up into his hand. “Sí, señor. Wherever you need me.”

Then the captain turned his attention to Horatio Korman and said, “You, come with me.”

To Mercy’s mild surprise, the ranger did not object. Instead, he immediately stepped into the aisle and replied, “I thought you’d never come around.”

The nurse saw where they both meant to go and she asked, “Come around to what? Where are you two going?” Instead of answering, they moved to the rearmost door and opened it. She followed, even though she had a feeling that one or both of them was on the verge of ordering her not to. Before the wind had died down from their crossing of the couplers and the gap, she had entered the caboose behind them and drawn the door shut, clipping off the wild, freezing air and sealing them into something like a very uncomfortable vacuum.

She turned around just in time to see Captain MacGruder level his service revolver at Malverne Purdue and tell him, “Out of the way, Purdue.”

But Purdue was already on his feet, Winchester in hand and aiming right back at him. He said, “No.”

The caboose was empty except for the five of them: Mercy, the ranger, the captain, Purdue, and the loyal Oscar Hayes, who looked like he’d rather be almost anywhere else at that particular moment. The silence that fell in the wake of the no was thick and muddled with the ambient roar of the train and the wind, and the occasional whistle of the incoming train and the Dreadnought itself, which finally saw fit to answer the Shenandoah.

The ranger had not yet drawn either of his visible guns, which had been returned to him after the last stop. But one hand hovered in a warning, prompting Mercy to wonder how she’d not yet noticed that he favored the left.

Without lowering his gun or so much as blinking, the captain said evenly, “Purdue, I know you’ve heard it. Have you seen it, out the window here?”

“Nope.”

“They’re gaining on us, and soon they’re going to catch us. If they beat us to the pass, we might be done for. Do you understand me?”

With equal deadpan delivery, the scientist said, “I do, but I believe my experiments are more important than a few casualties.”

“Believe what you want. That engine is moving four cars, and it’s pumping on a new draw-the same kind as our engine, but lighter and more powerful. That’s not fear, that’s a fact-isn’t that right, Ranger Korman?”

“That’s right. The V-Twin system will move that engine with almost twice the power of the one we’re riding now, and they’re pulling half the weight.”

“The Dreadnought can outrun them.”

“The Dreadnought is towing too much to outrun that Rebel sprinter,” the Texian insisted.

“Then we’ll shoot her off the tracks. I remain unconcerned,” said Malverne Purdue, who also remained ready to fire at the drop of a hat.

Horatio Korman said, “Maybe, maybe not. But if she gets ahead of us, and gets any lead on us-as she almost certainly will-they’ll take out the tracks and then we’re all of us dead.”

“We’ll blow it off the tracks before it passes us.”

His patience running thin, Captain MacGruder said, “It’s not going to get a chance to pass us, Purdue. We’re going to drop some weight and outrun it. We’ll beat it to the punch if we can shake some of our load; but we can’t let them get ahead. We’re all done for, if we do.”

Purdue said, “Well then, I guess we’re all shit out of luck, because you’re not unfastening this car,” he said, indicating with a thrust of his shoulder the rearmost vehicle, the hearse. “You wouldn’t do that, would you? You wouldn’t disrespect the war dead like that, would you, Captain?”

“Right now the needs of the living come first. Now, get out of the way, Purdue, and let us have a go at those couplers.”

“Over my dead body.”

“I’m not afraid to arrange it,” said the ranger, his hand still vibrating an inch over the butt of his gun where it jutted out of his belt.

The captain said, “The dead will have a lot of company if we don’t let that car go.”

Oscar Hayes had his gun out, but he didn’t know where to point it. He wouldn’t shoot the captain, surely, but his wrist was sagging in the direction of the ranger, just in case he needed to shoot someone. Purdue hadn’t budged. The captain and the Texian were so tense, they could’ve twanged like harp strings.

And the Dreadnought pulled them all closer to the pass with every second.

“What have you got back there?” asked the captain. “What have you really got, that’s what I want to know.”

“Dead people. That’s all.”

Mercy decided it was finally time to jump in. She said, “He’s moving a drug called yellow sap. He wants make a weapon out of it.”

Most of the eyes in the caboose and at least one gun shifted focus to aim right at her.

The ranger’s didn’t. He didn’t take his glare away from the scientist, because he already knew what was in the caboose. He added his right hand to his left, and now both palms dangled over both butts of both his guns.

She blurted out the rest. “The dead men back there didn’t die in war. They died from too much sap. But the stuff the sap’s made of-it does a whole lot worse! It makes people crazy, so they eat each other!”

The captain’s gaze whipped back and forth between them. He demanded of Purdue, “Is she telling the truth? Is she?”

Not quite rattled, but taken off guard, Purdue grumbled, “She doesn’t know a damn thing.”

Mercy thought maybe Horatio Korman would back her up, but he didn’t-perhaps because he wanted the scientist and his assistant to forget about him, and fight with the captain instead. So she defended herself, saying, “I do, Captain-please, you have to believe me! And you,” she said to Purdue, “if you want to prove me wrong, then show him what you’re hoarding back there!”

“I want to see your papers again,” the captain said to the scientist. “I want to see who processed them, and who signed them, and-”

“What difference does it make?” demanded Purdue, changing his approach. “Yes, we’re making weapons-that’s what armies do! What’s carried in the last car is important to our program-more important than anything we’ve ever been able to create so far. The potential,” he said, pleading now, almost. “You have no idea what potential.”

Mercy said, “Just this once, Mr. Purdue’s right, Captain. You have no idea of the potential. You have no idea what it does to people-what it could do to the South, yes, but what it could do to anyone. Anywhere. The gas that makes the sap, it kills without caring what uniform anybody’s got on.”

The captain weighed this, even letting his guns lower a fraction of an inch while he thought. He said, “I have my orders, too, Purdue. And I have my men to protect, and you’re not one of my men. Those dead fellows in the back, there’s nothing I can do for them now-and if the Union wants its weapon, the Union can send somebody back here for that cargo. They can forgive me later, or court-martial me if they’d rather, because by God, we’re-”

Purdue’s posture changed ever so slightly, and at the same time his fingers made the slightest jerking motion. But before he could interrupt the captain with a bullet through the heart, Horatio Korman’s guns were in his hands-both of them, faster than a gasp. He fired them both, one at Oscar Hayes, and one at Malverne Purdue.

Hayes went down without a sound, and Purdue’s rifle muzzle flew skyward, firing one outstandingly loud bullet straight through the ceiling.