Story and Setting
The Expanse: Osiris Reborn is set during the events of the first two books in the series, Leviathan Wakes and Caliban's War, which roughly correspond to seasons one through three of The Expanse television show. This is a period of escalating tension between Earth, Mars, and the Belt, with the discovery of the protomolecule acting as the catalyst for a solar-system-wide crisis.
The World of The Expanse
By the time of the game's events, humanity has colonized the solar system but has not left it. There is no faster-than-light travel and no contact with alien civilizations (yet). Human civilization is divided into three major factions: Earth's United Nations, the Martian Congressional Republic, and the Outer Planets Alliance representing the Belt. These three groups are locked in a cold war that threatens to turn hot at any moment.
Life in the solar system is governed by physics. Travel between planets takes weeks or months, not hours. Acceleration is measured in g-forces that can crush the unprepared. Gravity on stations is generated by spin, not magic. Resources are scarce, especially in the Belt, where water and air are commodities that people kill for. This grounding in realistic science fiction is what sets The Expanse apart from most space opera settings, and the game reflects that tone.
The Player Character
The player takes on the role of a Pinkwater Security mercenary stationed on Eros Station. Pinkwater Security is a private military company that contracts with corporations and governments across the solar system. The player character's background is determined by their chosen origin (Earther, Martian, or Belter), which affects both the narrative context and how other characters react to them throughout the game.
The game opens with the player on a routine assignment on Eros when the protomolecule incident begins. The station descends into chaos, and the player barely escapes alive aboard a stolen Protogen vessel: the Gemini. This ship becomes the player's mobile base for the rest of the game.
Jay and the Crew
The player does not escape Eros alone. Jay, the player character's twin sibling, is the first companion to join the crew. Jay shares the player's origin and has a deep personal connection that grounds the early story in emotional stakes. Shortly after escaping, the crew picks up Zafar, a former MCRN engineer whose technical skills prove essential for keeping the Gemini operational.
Over the course of the game, additional companions join the crew as the player travels to different locations across the solar system. Each new companion brings their own background, motivations, and potential storylines. The crew dynamic aboard the Gemini is one of the game's central storytelling pillars.
The Protomolecule Conspiracy
The main narrative revolves around the protomolecule, an alien substance with the ability to fundamentally restructure biological matter. The protomolecule was discovered by Protogen, a powerful megacorporation with connections to inner-planet governments. Rather than disclosing the discovery, Protogen began experimenting with the substance in secret, including conducting horrific tests on human subjects.
The incident on Eros is one of these experiments gone wrong (or perhaps gone exactly as Protogen intended). As the player investigates what happened and why, they are drawn deeper into a conspiracy that involves corporate black sites, military cover-ups, and political manipulation at the highest levels.
Project Caliban
One of the threads the player uncovers is Project Caliban, Protogen's program to create protomolecule-human hybrids as weapons. These Caliban subjects are encountered during the game as enemies, and they represent some of the most dangerous threats the player will face. The project ties into the events of the second book, Caliban's War, and connects the game's story to the broader lore of The Expanse.
The Caliban subjects are not mindless monsters. They are the result of deliberate experimentation, and the ethical horror of what was done to create them is a recurring theme. Encountering a Caliban subject is meant to feel different from fighting ordinary human enemies; these are something else entirely, and the game's tone shifts when they appear.
Player Choice and Consequences
Dialogue choices are a core part of the storytelling. Conversations with NPCs, companions, and faction representatives offer branching options that affect how the story unfolds. Some choices have immediate consequences (angering an NPC, unlocking a side quest, losing access to a vendor), while others have ripple effects that only become apparent hours later.
The developers have emphasized that the game is not a simple good-versus-evil morality system. Choices are often about competing loyalties, pragmatic trade-offs, and deciding which faction's interests align with the player's goals. Helping the OPA might alienate Earth-aligned contacts, but refusing to help might cost the player access to Belt resources and information.
The most significant choices tie into the companion permadeath system. How the player treats their crew, which missions they prioritize, and how they handle critical story junctures all contribute to determining which companions survive the story.
Timeline Placement
For fans of the source material, the game's story runs parallel to the events of the first two books. The player is not James Holden or any of the main characters from the novels. Instead, they are a separate character operating in the same universe during the same period. This means that major events from the books (the Eros incident, the Ganymede crisis, the discovery of the Ring) form the backdrop of the game's story without requiring the player to step into the shoes of an established character.
This approach allows Owlcat to tell an original story within a well-established setting. Players familiar with The Expanse will recognize events, locations, and occasionally characters from the source material, while newcomers can enjoy the game as a standalone science fiction narrative.