Avasarala is blindsided while on a visit to Mars. The Roci crew continue their protomolecule investigation while tensions between the RCE and Belters reach a tipping point. Drummer and Ashford track down a terrorist.

Drummer and Ashford confront a dangerous person from Naomi's past. Murtry hunts down a target. Bobbie's makes a life-changing confession.

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.

Avasarala faces fallout for the UN's military mission. Ashford and Drummer makes big decisions about their future within the OPA. A spreading illness on Ilus takes a toll on Amos. Alex and Naomi's attempt to rescue the Barb turns desperate.