Zahara is a talented airship engineer living in a post-war Baltimore in the future. She has a well-paying job working on airships, but after a tragic accident caused by incompetent engineers ends with a death toll in the hundreds, Zahara and her former boss Porter decide to leave for San Fransisco, a town that will better appreciate skilled workers. Porter is also a very talented engineer, and a thoughtful person who writes all of his thoughts in a closely guarded journal that even Zahara, who he trusts dearly, is not allowed to read.  Their funds are very low since they don’t have stable jobs, but they meticulously save their money for months to buy passage on a wagon train that will take about a month to get them to San Fransisco. Zahara always dresses like a man, Baltimore and the train they will board is often very dangerous for women even when accompanied by a man. They board the train, and remain on it for nearly a month before deciding the travel is not worth the treacherous journey. The train is lawless- there is thieving, shooting, sexual assault, and constant hostility and hardship. They want a refund for the last stretch of their journey, and to stop in Chicago to make the rest of the journey later. But the wagonmaster, or the conductor of the train, denies them their refund. Since the cost of their trip is so dear, they can’t afford to not go the rest of the way. 

After a couple more days, they run into “Indian” territory, which is considered hostile. Just before they ride into it, the train stops for food and water. While Zahara cleans the quarters that she and Porter share, she ends up reading Porter's journal. She discovers that he's been drawing incredible and brilliant inventions. Porter walks in on her, but doesn't notice the book because she is also holding a Jane Austen book. She panics and shoves them both in her coat pocket before leaving the train with him.

Outside the train, people are preparing to eat what they can find outside- berries and whatever small animals they can snare. But apparently, someone who lives nearby where they stopped donates a feast’s worth of rabbits for them to eat. The train passengers feast on the rabbits, all having a good time. Zahara doesn’t like the idea of eating rabbit, so she gives her portion to Porter. They all fall asleep outside the train.

The next day, the train is gone and so are all of their belongings. Everyone is extremely ill except Zahara but especially Porter. At first, the passengers, who are all as desperate as Porter and Zahara, believe that maybe the wagon master left them to refuel. But Zahara knows the wagon master was never to be trusted, and that they were stranded on purpose. But it takes everyone else two days to realize their predicament, and turn against one another. Porter’s condition worsens, and the doctor on the train figures out that they were poisoned by the rabbit they were given, likely by the wagonmaster's doing. They were meant to die, but the tonic that one of the passengers had shared that night kept them from dying. Porter is in bad shape because of the double portion given to him by Zahara. The doctor tells Zahara that she could help him by collecting a plant he had seen a little ways away. She leaves, but when she comes back, people have started scavenging, and people had taken Porter’s boots, coat, blanket, and food while he lay prone. Zahara is furious when she sees this. She points her pistol at the thieves and manages to get his clothes and blanket back, but nothing else. The rest of the passengers run off, leaving the pair alone with hardly any supplies. 

Zahara and Porter decide to go north, despite Zahara believing it to be a dangerous idea seeing as there are more Indians that way. But Porter insists. Porter only makes it half way before his illness gets the better of him; he tells Zahara that he won't survive another day, and that she should go without him. Zahara does go without him, but not with the intention of accepting his death. She follows his directions to find the Sioux tribe of Native Americans. He had told her to make noise to attract their help, but cautioned her to approach them calmly, not to shoot her gun toward their land to get their attention or they would think she was aggressive. But after not getting a response from shooting her gun in the air, she shoots toward their land to get their attention. This gets their attention but causes them to capture her violently, beat her, rip up her clothes, and find the books she had hidden in her pockets, including Porter's journals. They rip up both books while they question her, until they realize she only needed help and was not an aggressor. The Sioux sends a group to find Porter while they patched up Zahara. The Jane Austen book is returned, but not Porter's journal. Zahara asks the woman helping her, Mataka, about it, and she says she didn't know but would ask about it.

Later, a Sioux named Igmutaka shows her around where the Sioux are living, and shows her that they have engineered their own airships, one of which is called the Iron Cloud. He explains that it is named that after an engineer who built it. But Iron Cloud was accused of treachery and was forced to leave the Sioux. Later on it came out that Iron Cloud was innocent, but it was too late to try to find him again. Zahara hears Porter laughing in a different room and immeidately goes to find him. As they reunite, Igmutaka reveals that Porter is Iron Cloud. Igmutaka and Mataka are old friends. Zahara notices unhappily that Mataka is flirting with Porter, and Mataka gives Zahara a look meaning to wound her about it. But when Zahara and Porter are given time to reunite alone, Porter makes his feelings for Zahara known. While Zahara is annoyed that she feels Porter lied about his identity, they become more than friends in that moment.

However, Igmutaka comes in and reveals to both of them that Porter's jounral is missing, Porter is furious that Zahara had it in the first place, and Zahara is forced to explain herself. But it is worse than Zahara thought it would be — Igmutaka reveals that he had given the jounral to Mataka to give back to Zahara along with the Jane Austen book — she had it all along but told Zahara she didn't know where it was. Porter and Igmutaka explain that Mataka is thirsty for war against the white Europeans. She wants to protect the Native American land, but her plans are not realistic and would likely cause a tit for tat that the Native Americans would lose in the end. Igmutaka believes that Mataka stole Porter's journal to sell them to further her aims.

Igmutaka, Porter, and Zahara leap into action to go after Mataka in an airship.