“It sounds awful, but I don’t guess I’d put it past him.”

“Neither would I,” Miss Clay said with a set of her mouth that wasn’t quite a smile, but conveyed the fact that she thought that now she and the nurse might finally be on the same page. “And that’s why we must take this opportunity while the train is stationary, to sneak into that rear car and see what’s inside.”

Mercy’s eyebrows bounced up. “You can’t be serious.”

“Of course I can. I’ve even changed my shoes for the occasion.”

“Bully for you,” Mercy said. “What are you going to do? I’ve already done my best to persuade the captain to intervene. Shall you seduce your way past Mr. Purdue and-”

“Don’t be revolting. And please recall, I’ve requested your own involvement as well. It’ll be disgusting, no doubt. And it wouldn’t be necessary if that blasted captain would stand up to the hierarchy and insist for himself that the things under his purview are all known quantities. But alas, I can’t convince him to budge on the matter. Ridiculous man, and his ridiculous sense of duty.”

“He’s all right. You leave him alone.”

Miss Clay made a little sniff and said, “If you say so. Now, come on.” She changed the subject, rising to her feet. “You and I are going to perform some reconnaissance.”

“We’re going to do what?”

“We’re going to poke around, and let ourselves into that car.”

Mercy asked, “How? The doors are sealed and chained. You’ve seen that yourself, I bet, when we’ve stopped at stations and stretched our legs. And even if they weren’t, Mr. Purdue and his very large gun are standing between us and that car. Or, Mr. Hayes, as the case may be.”

“Think bigger. Think higher.” She pulled on a pair of thin calfskin gloves and fastened their buttons while she said, “We’ll go over. There’s an emergency hatch on the roof. It’s designed to let people out, not in, but unless I’m sorely mistaken, it will work both ways.” Finished with her gloves, she continued, “Here’s what we’ll do: We’ll go to the last passenger car, take the side ladder up to the roof, and crawl across the top of the caboose, then jump over to the final car.”

Mercy said, “You’re daft!” but she was already getting excited about the plan.

“I’m daft, and I’m going. And I require your medical . . .” She almost didn’t say it, but in the transparent hope that flattery might get her someplace, she finished with, “expertise.”

“Oh, for the love of God.”

“Please, Mrs. Lynch. The repairmen are finished with the rear compartments, and they’ve moved on to the engine and the broken windows in the first car. We won’t be here more than another hour.”

Mercy said, “Fine,” folded her satchel up, and left it on her seat. She rose and adjusted the gunbelt she now wore more often than not and draped her cloak over her shoulders without raising the hood.

As she followed Theodora Clay out of their passenger car and onto the next one, she did not mention that their errand might prove to be a race against time. She did not tell her companion about the Shenandoah, the Confederate engine that had ridden a northwestern track in order to bring those meat-baskets up to the plains and unleash them on the Dreadnought. She did not mention that she had indeed been talking to the Texian, and that he believed the Shenandoah was still following, tracking to the south and east, but closing ground, despite its defeat. If he was lucky, Horatio Korman was in the process of retrieving a telegram that would inform him of how correct his suspicions were. And if they were all lucky, it would say that the Shenandoah had given up, turned around, and headed back down to Dallas.

Meanwhile, the engine halted in Denver for only a few hours when it ought to have stayed overnight for an inspection; because a telegram from Union intelligence had been waiting in Denver, no doubt warning of precisely this same possibility and urging haste in any repair work.

While the train sat there, grounded and undergoing the improvements that would keep it rolling the next thousand miles, Mercy Lynch followed Theodora Clay to the spot between the last passenger car and the caboose. It was strange to stand on the junction without the wind putting up a fight, but no stranger than watching Miss Clay scale the external ladder with casual quietness and then, from the top of the car, pivot on her knees and urge Mercy to join her.

When she reached the top rung, Miss Clay whispered, “Move slowly and be quiet. Discretion is the better part of valor in this instance. If we make too much noise, they’ll hear us inside.”

“Sure,” said Mercy, who then pulled herself up on top of the steel-and-tin roof, sliding on her belly like a seal and then climbing to an all-fours position. Her skirts muffled the knocking of her knees, and her wool gloves kept the worst of the frigid surface’s chill from getting through to her fingers. But even with the thick layers of clothes, she could feel the cold seeping up through the fabric, and onto her shins, and into her palms.

The nurse had the feeling that Denver was a gray, smoky place under the best of circumstances, and while the Dreadnought was being addressed in its station, a layer of dirty snow hung over everything. It blurred the edges between buildings, sidewalks, streets, and interchanges, and it made the air feel somehow colder. Atop the caboose, which they very slowly traversed in inches that were gained in calculated shifts, slides, and steps, there was little snow except what had fallen since they’d stopped. This snow was a funny color, more like frozen smog than shaved ice. It collected between her fingers and soaked along her legs and elbows where it met her body heat.

Around the train, men hurried back and forth-most of them soldiers or mechanics, bringing sheets of glass and soldering equipment up to the front of the train; but over the edge Mercy could also spy a station manager with stacks of envelopes, folders, ticket stubs, and telegraph reports.

All she could do was pray that no one looked up.

Even if the women flattened themselves down, anyone standing close enough to the caboose could likely stand on tiptoe and see what they were doing. The crawl was torturous and time consuming, but in what felt like hours (but was surely only ten minutes) they had traversed the car and were prepared to lower themselves back down onto the next platform, the one between the caboose and the final car.

On her way down the ladder, Theodora Clay hissed, “Mind your step. And stay clear of the window.”

Mercy had every intention of following these suggestions to the letter. She slowly traced Miss Clay’s steps down the ladder, across the pass, and then up the next ladder, approximately as silently as a house cat wearing a ball dress. On her way to the top of the final car, she looked over her shoulder to peek through the caboose window, where she saw the back of Malverne Purdue’s head bobbing and jiggling. She thought he must be talking to someone she couldn’t see, and hoped that she wasn’t in the other speaker’s line of sight.

By the time she was situated and stable, Theodora Clay was already prodding at the edges of the emergency hatch, or ventilation hatch, or whatever the portal’s original purpose might have been. Mercy crept to her side and used the back of her hand to brush the small drifts of snow away from the hinges and seal. Before long, she spotted a latch.

Mercy angled her arm for better leverage and gave the latch a heave and a pull, which Theodora Clay assisted with when the nurse’s progress wasn’t fast enough to suit her. Between them, they forced the handle around and then heard the seal pop, its rubber fittings gasping open.

Theodora Clay asked, “Why would they seal it with rubber, like a canning jar?”

Mercy was already rocking back on her knees, her hand to her face. “To keep the cold in. Or . . . good God. To keep the smell contained! Lord Almighty, that’s . . . Ugh,” she said, lacking a word with the appropriate heft and reaching instead for a gagging noise.