Kady Grant is the protagonist of the novel. She is a teenage survivor of the Kerenza assault and the daughter of Helena Grant, a doctor working aboard the Copernicus, and Isaac Grant, an engineer on the Heimdall Jump Station. Kady is the romantic partner of Ezra Mason and learns to be a hacker with the help of her mentor, Byron Zhang, onboard the Hypatia.

Kady presents as gruff, abrasive, agile, adept, and cunning. Deep down, she is highly emotional and in denial of her feelings. She makes difficult decisions that at best would land her in prison and at worst would get her killed in horrible ways, but she does so with a brave face. She starts out as cocky about her abilities and is openly hostile toward others, but as the story goes on, she learns how to play her cards better and leave space for her feelings while still being snarky. Kady is bold and reckless, but she does everything with the good of others in mind.

Ezra Mason is an 18-year-old survivor of the Kerenza assault whose dad, a miner, passed away in the initial attack. He is the romantic partner of Kady Grant and a second lieutenant pilot onboard the Alexander.