Jim Holden is an Earther who grew up on a family co-op in Montana with eight parents. Discharged from the UN Navy for refusing to fire on an unarmed ship, he finds a comfortable routine on the Canterbury. When his crew answers a mysterious distress signal, his uncompromising idealism thrusts him into a system-wide political crisis. He prefers transparency over political maneuvering, often broadcasting sensitive information with little regard for the strategic consequences.

Joe Miller is a Belter and a seasoned detective working for the Earth-backed security firm Star Helix. Weary and jaded, he uses alcohol to cope with a growing sense of purposelessness in his career. His assignment to track down a missing Earther heiress soon becomes a personal obsession that challenges his cynical worldview.

Naomi Nagata is a Belter who serves as the brilliant chief engineer of the Canterbury. She possesses immense technical skill and acts as the practical backbone of her small crew. Though she keeps her past heavily guarded, she forms intense bonds with her found family and regularly serves as a critical sounding board for Holden.

Amos Burton is an Earther mechanic who grew up in the harsh environment of Baltimore. With a tough background that stunted his emotional development, he relies entirely on those he trusts to dictate right from wrong. He serves as the crew's muscle and is fiercely dedicated to Naomi, recognizing her as his ultimate authority.

Alex Kamal is a Martian pilot with a background in the Martian Congressional Republic Navy. He left his family on Mars to pursue his deep passion for flying. While he occasionally struggles with fear outside the cockpit, he transforms into an exceptionally skilled operator at the helm of a ship.

Julie Mao is the rebellious daughter of a wealthy Earther corporate magnate. Rejecting her privileged upbringing, she relocates to the Belt to work as an activist for the Outer Planets Alliance. Her sudden disappearance sparks a massive investigation that uncovers a dangerous conspiracy threatening the entire solar system.

Dresden is an executive scientist working for Protogen. He oversees highly unethical experiments with a mysterious substance, displaying a sociopathic disregard for human life in his pursuit of evolutionary advancement.

Fred Johnson is a former UN Marines officer infamous as the "Butcher of Anderson Station" for his role in a violent suppression of protesters. Plagued by guilt over the massacre, he resigned his commission and shifted his allegiances to the Belters. He now leads the Outer Planets Alliance from Tycho Station, using his military expertise to legitimize the Belt's political standing.

Havelock is an Earther working as a security officer for Star Helix on Ceres Station. Working alongside Miller, he faces constant prejudice and open hostility from the local Belter population, which limits his effectiveness as a police officer.

Anderson Dawes is an influential Outer Planets Alliance operative operating on Ceres Station. He maintains a delicate balance of power between the official authorities and the Belter underworld, carefully managing OPA interests as political tensions rise.

Captain Shaddid runs the Star Helix security precinct on Ceres Station. She balances corporate contracts with the daily realities of policing a restless Belter population, routinely making decisions based on political optics rather than actual justice.

Jules-Pierre Mao is the head of Protogen, a massively wealthy Earth-backed corporation. He uses his immense resources and influence over private security firms to track down his estranged daughter, setting the entire narrative in motion.