To which he replied pointedly, “Last I heard, Pinkertons were civilians as well, ma’am, and you profess to work on behalf of the District yourself. And I don’t believe I caught your name, but I know your accent isn’t any farther north than the line.”

“Maria.” Then she swallowed hard and said, “Maria Boyd. I come from Virginia, but I work from Chicago.”

If he recognized her name, he didn’t react to it. All he said was, “All right, then, Miss Boyd and Mr. Epperson. You know an awful lot about what we’re doing.”

“More than you do,” she said urgently. “Please, you have to listen to us, Captain … Captain, I don’t believe I caught your name, either.”

“MacGruder,” he told her. “I’m commanding officer for this operation, such as it is,” he added unhappily, gazing toward the trapped rolling-crawler.

“Captain MacGruder,” she said, turning the name over in her mouth, feeling the letters tumble together and thinking that it sounded familiar—very familiar—but she couldn’t put her finger on it. Finally, she gave up and asked, “Do you know what the weapon does?”

He hesitated. Maria thought that it must not be that he didn’t know, but that he wasn’t sure how much to tell her. “It’s a bomb. An advanced bomb that will do … untold damage.” He said it like he was confessing to himself. “But it’s a bomb that can end the war, like the president wants—and that is my mission. These are my orders.”

“No, sir, that isn’t your mission, and your orders were falsified. That weapon is a bomb, yes, and it will do far worse than untold damage—but it won’t end the war, you can safely bet on that. Katharine Haymes is readying herself to make a fortune on a gamble that this bomb works well enough to become the talk of the town, but not well enough to end a goddamn thing.”

“Haymes?” The captain looked startled. “That’s a name I know.”

Henry said, “You ought to. She killed hundreds of Union prisoners at a camp in Tennessee.”

“With gas,” he said thoughtfully. “She did it with gas; I heard about that. I tried to tell people, but they didn’t want to hear it.…”

“Hear what?” Maria asked. “Tell people what?”

He shook his head. “I told my superiors that I’d seen that kind of devastation before. I’d reported it once already … not that anyone listened then, either. What she did, that weapon she tested.… But, wait, I thought she was a Confederate?”

Maria shook her head. “No, she claims no nation. She belongs to whichever side can pay her best, and we both know that means she’s working for the Union now. That thing you accompany, it’s a gas bomb of such a size that it could wipe out half of Atlanta, including whoever’s nearby when it’s released. You’ll never escape it. There won’t be time.”

“But, the cargo ship…” The soldier with the rifle asked the captain, “The ship’ll pull us out, won’t it?”

“How?” Maria demanded, addressing him once more, rather than the handsome captain. “That thing isn’t big enough to hold the lot of you, and someone would have to stay behind and set the bomb off, anyway.”

The captain argued with her, but without much conviction. “We’re going to shoot it from the air. It’s a big enough target. But … I’ve wondered.” Then he muttered, like he couldn’t shake the significance, “If it’s … a gas bomb…”

“And one that doesn’t just kill…” Henry continued.

“It’s the walking plague.” The captain said the words softly, almost under his breath. “It’s a bomb that gives people … that turns them into the living dead. That’s what this is, isn’t it? The walking plague is created by a weapon.”

“Well, yes and no,” Henry said. He might’ve said more—asking how the captain had drawn such a conclusion, correct though it might well be—but at that moment Maria had a revelation.

Two thoughts had been bouncing around in her brain, ever since the captain had identified himself: his name, and where she might’ve heard it before. Those two ideas finally collided, crashing together so that the sparks illuminated the truth. She blurted out, “You’re the Captain MacGruder from the nurse’s notes!”

Everyone froze, mostly from confusion. The captain asked her, “I’m sorry, nurse? What nurse?”

“On the train,” she continued excitedly. “The Dreadnought—you were on the Dreadnought! I read about it!”

He recoiled, stunned. “Read about it? Where on earth could you have read about it? No one’s written about it except for me—and what I wrote went ‘missing,’ according to anyone I asked,” he said angrily. “I tried to tell them! The walking plague doesn’t just walk among soldiers, and it isn’t confined to the front.”

“But it is you,” Maria persisted. “You were the Union captain the nurse trusted, who survived what happened in Utah. Just admit it!”

“The nurse,” he muttered, flailing to find the context she prodded him for. “There … there was a nurse, yes. Mercy, that was her name. She … she wrote a book? She’s alive? I tried to find her, but the ranger, the nurse, the Rebs who made it out alive … everyone’s gone. Reassigned, they told me,” he recounted bitterly. “Secret missions. Secrets everywhere, no one talking, no one listening. No one left. All of them, gone.”

“And you’ll be gone, too, if you finish this mission. We all will.”

The forest whistled and shook, as the wind gave one last gasp through the trees, scattering what was left of the leaves and tweaking the brittle branches. No one spoke while they watched the captain reflect, consider, think, and finally … conclude.

He gave a good, hard glare at the cargo ship through the trees and said, “Get me Frankum. I need to speak with him. You two—Miss Boyd, Marshal—come with me. Graham, Simmons, keep an eye on them.”

Maria began to protest. “But we’re—”

“I’m not taking any chances.”

So, at gunpoint, they followed the captain up the side of the hill, onto the road, and into the middle of the caravan—where they were greeted with stares and gossipy whispers.

The captain announced, “Gentlemen, we have guests: a U.S. marshal and a Pinkerton agent, pulled from the woods like foundlings. They were left there courtesy of Captain Frankum, or so they tell me. So, where is our fine, upstanding dirigible pilot, eh?”

Something about his pronunciation of “fine” and “upstanding” implied a keen sense of irony.

Maria and Henry kept close to each other, nearly back-to-back. No one had taken their firearms, which might be construed as a lack of caution on Captain MacGruder’s part, except that they had nowhere to go, and they weren’t likely to stage a gun-blazing escape in their battered state.

“You two, over here,” one of their guards told them, gesturing with the barrel of his gun. He guided them to the big rolling-crawler, and suggested they should stand against it and wait for further instructions. “Captain? Where are you going?”

“I’ll be back in a minute,” he answered vaguely, and stomped off to the far edge of the convoy, where Maria could no longer see him.

She didn’t like it, and Henry didn’t, either, but they did as they were told. They put their backs to the thing and tried not to think about what was inside it, now only inches from their bodies. Maria fancied that she could hear a hum, some strained, coursing sound from within. She could feel it better than she could hear it, as the vibrations rattled at her ribs. It was almost as if the bomb were a living thing, with pulse and respiration and a sense of urgency—an awful destiny that it wanted to fulfill.

Maria banished her imagination’s wanderings and closed her eyes, exhausted. She wanted to sit down, but she couldn’t bring herself to do so, not while so much danger remained … and she didn’t know what form it was likely to take, or even where it might come from.

But she was so, so tired. And so very sore. And she so very badly wanted to sleep.

Eventually, Captain Frankum appeared in their midst, joined by two of his fellow airmen. The captain himself was a short, sturdy man without an ounce of fat on him, but a squared-off appearance that indicated a great deal of muscle. He was no more handsome or friendly looking up close than he had been in the clouds, nor were either of his men.

Captain MacGruder also returned from whatever errand he’d wandered off to. His face was set in a firm expression, all business and ready for conflict—an effect that was slightly undone, in Maria’s opinion, by the pink flush across his nose, brought on by the cold.

“Frankum, there you are. I’ve got a question for you,” he said.

At approximately that precise moment, Frankum noticed the newcomers. At first, his eyes glanced past them, but he did flash a quick second look at Maria. It could’ve meant anything: He might have recognized her from the sky, or maybe he was only confused at seeing a woman there.

“Who are they?” the Baldwin-Felts man asked.

Captain MacGruder feigned innocence. “You don’t know?”

“No, I don’t.”

“Then why’d you shoot them down a few hours ago?”

“Why did I…?”

“You heard me,” MacGruder said, coming in closer. He leaned forward, craning over the shorter man and casting a shadow over him. “Why did you shoot them down? What we have here, Captain”—spitting out the word like it tasted bad—“is a U.S. Marshal and another agent, sent as messengers from the White House.”

Maria appreciated that he’d left out the “Pinkerton” part, given how little love was lost between the two firms. It meant he was thoughtful for her safety, perhaps; or it meant that he was smart, and didn’t feel like adding the extra trouble to the mix.