In The Expanse season 3, the entire solar system was changed forever when the Protomolecule led James Holden to an alien space station and manipulated him into triggering a system of ring gates that allowed instantaneous travel across the galaxy. As entire new worlds open up before Inners and Belters alike, Holden is living with the Miller-shaped ghost of the Protomolecule, whose primary motivation is to find out which deadly ancient civilization wiped out its makers billions of years previously.
The Rocinante Crew
Steven Strait as James Holden - The Expanse’s initially reluctant protagonist has finally accepted his role at the center of the galaxy’s future and captains the Rocinante to further investigate the mysterious Protomolecule, driven by visions from The Investigator.
Dominique Tipper as Naomi Nagata - One of the Roci’s engineers and now officially in a relationship with Holden, Naomi still struggles to reconcile her new Inner friends with her Belter roots, both physically and mentally.
Wes Chatham as Amos Burton - Best known for his role in the Hunger Games sequels, Amos remains a black-and-white, volatile figure, but is loyal nonetheless. His upbringing and mental state remain somewhat ambiguous.
Cas Anvar as Alex Kamal - No longer just a glorified bus driver, Alex remains the upbeat glue that keeps the Rocinante’s crew together, and is usually the one to get his friends out of hot water when needed.
Returning Characters In The Expanse Season 4
Thomas Jane as Joe Miller/The Investigator - Miller was absorbed by the Protomolecule in The Expanse season 2 and now appears in Holden’s mind to guide him. This sentience is investigating what wiped out the ancient race responsible for building the Protomolecule.
Shohreh Aghdashloo as Chrisjen Avasarala - The foul-mouthed, forthright politician has now been promoted to Secretary General of the U.N., and season 4 finds her desperately trying to prevent an exodus through the ring gates. Shohreh can be seen playing a very similar character to Chrisjen in Star Trek Beyond.
Frankie Adams as Bobbie Draper - After exiting the Martian Marines in not-so-magnanimous circumstances, Bobbie finds herself adjusting to civilian life on Mars, while still hankering for a more meaningful lifestyle.
Cara Gee as Drummer - After surviving being crushed in The Expanse season 3, Drummer remains captain of the Behemoth, tasked with patrolling the newly-opened ring gates. Despite a truce, Drummer must navigate lingering political tensions from the Belt.
David Strathairn as Klaes Ashford - Serving alongside Drummer on the Behemoth, the duo appeared to settle their differences in The Expanse’s third season, but can Ashford really be trusted?
Chad L. Coleman as Fred Johnson - Most familiar to viewers as Tyrese in The Walking Dead, Coleman returns as O.P.A. leader, Fred Johnson, in a recurring role.
New Characters In The Expanse Season 4
Burn Gorman as Murtry - Gorman has appeared in everything from The Dark Knight Rises to Torchwood, and The Expanse finds him portraying a military-minded Earthling representing the Royal Charter Energy company, assigned with exploring the world beyond the gates.
Lyndi Grennwood as Elvi Okoye - Like Murtry, Okoye has been sent as part of RCE to study Ilus, an Earth-like planet beyond the ring gate. Unlike her boss, however, she takes a more scientific approach. A key character from the books, many Expanse fans have been looking forward to Okoye’s arrival.
Keon Alexander as Marco Inaros - A militant O.P.A. faction leader, Inaros has personal links to Naomi and is none too pleased at how his brethren have aligned with Earth and Mars to police the ring gate.
Other inclusions in The Expanse season 4 include Nadine Nicole as Clarissa Mao, Rosa Gilmore as Lucia Mazur, Jess Salgueiro as Chandra Wei and Lily Gao as Nancy Gao.
More: The Expanse Complete Timeline Explained
