The final battle between Earth and Mars threatens the very future of humanity. A new monster is unleashed on Prospero Station. Anna receives the smoking gun she needs.

New alien threats emerge on Ilus as Naomi battles health challenges on the planet. Bobbie searches for a missing person on Mars. Avasarala faces a new challenge in the UN.

As tensions on Ilus reach a boiling point, Holden reveals a secret. Avasarala debates Nancy Gao while an emergency on the Roci forces Alex and Naomi into action.

The Roci crew prepares for an incoming disaster on Ilus. Ashford and Drummer close in on an enemy within the Belt. Bobbie takes on a dangerous job.