The Expanse is a science fiction television series that premiered in 2015. The first season consists of 10 episodes and is set in a future where humanity has colonized the solar system but is divided into three major factions: Earth, governed by the United Nations; Mars, a militarized independent republic; and the Belt, the impoverished asteroid belt and outer planets, whose inhabitants are called Belters.
The narrative begins with the mysterious destruction of the Canterbury, an ice-hauling freighter traveling from Saturn to the Belt. The sole survivors are its executive officer, Jim Holden, and four crewmates. Holden publicly broadcasts a message accusing an unknown Martian ship of the attack, escalating tensions between Mars and the Belt to a boiling point. Meanwhile, on Ceres Station, a hardened Belter detective named Josephus Miller is tasked with finding a missing young woman, Julie Mao, a rebellious daughter of a wealthy Earth industrialist.
As the season progresses, these two seemingly unrelated stories converge. Holden’s crew, aboard the salvaged Martian gunship they name the Rocinante, evades various forces trying to kill them and discovers a derelict ship called the Scopuli. There, they find a strange, infectious proto-molecule. Miller’s investigation leads him to discover that Julie Mao was connected to a radical Belter faction called the OPA and that her path also intersected with the Scopuli. The conspiracy ultimately points to a secretive Earth corporation, Protogen, which is illegally experimenting with the alien proto-molecule, using it as a bioweapon on the unsuspecting population of Eros Station.
The season’s climax occurs on Eros, where Holden and Miller finally meet. They find Julie Mao, who has been tragically infected and killed by the proto-molecule, which is now transforming the entire station and its inhabitants in horrifying ways. In a desperate act, Miller sacrifices himself to steer the infected Eros on a collision course with Venus, preventing it from reaching Earth and containing the immediate threat. The season ends with the proto-molecule crashing into Venus, leaving its ultimate purpose and future a terrifying mystery, while the political fallout from the Canterbury’s destruction and the Eros incident sets the stage for an impending interplanetary war.