The crew of the Roci investigates a strange protomolecule ruin on an alien planet. Bobbie copes with civilian life on Mars. Drummer and Ashford battle with piracy in the Belt.

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

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.

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.