Dust is the final novel in Hugh Howey's Silo series. Dust picks up where the last novel in the series stopped, where it was revealed that there are other silos out there. This forces the silo inhabitants from the previous novel to confront the truths of their existence and the lies that have maintained the status quo for so many generations.
Dust follows Juliette, a mechanical engineer called to leadership after she escaped Silo 18 with the knowledge of the outside world and the history of the silos. After she returns home, she is forced to save her home in the face of seemingly insurmountable odds. To do so, she works with Lucas, who is able to decipher the secrets of the silo's servers, which hold the key to their past and, possibly, the path to their future.
Meanwhile, in Silo 1, the command silo, Donald, a former congressman, struggles with the morality of the silo system he helped create. He doesn't realize the sheer power the leaders of the silos have accumulated. As he uncovers the full extent of the machinations of those in power in the silos (all of whom use the silo for negative purposes), he works to undo the harm he has caused and, ultimately, to reveal the truth to all silo citizens about what the silos truly are.
For much of the novel, Juliette attempts to dig and get to Silo 17. Initially, people thought Silo 17 was dead. However, Juliette knows that her friend Solo and her children live there and are alive. Complicating matters is the fact that Juliette's silo is on the brink of a civil war. And each faction in that war thinks that she poses an existential threat to them. To curb this threat, Juliette allies herself with several people, who in turn ally themselves with others as tension rises.
In the end, Juliette, Silo 18's leader, manages to succeed in her mission to create a connection between her silo and Silo 17 by digging. There, she finds her friend Solo and the young children who see him as a father figure who is prospering against all odds.
In Silo 1, Donald, who has become fully aware of the enormity of the silo conspiracy and the manipulation of the truth by those in power, decides to take a final stand. He releases a deadly gas into Silo 1, eliminating the corrupt leadership of the silos but killing himself in the process.
Ultimately, the members of each silo start to communicate with each other. They forge new friendships and help each other recover from their recently destroyed world—one with a toxic atmosphere that once rendered it uninhabitable but is slowly recovering.
