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

Alex and Naomi work to keep the Barbapiccola in orbit amidst a power outage; Avasarala faces a tough decision; Holden and Elvi race to find a cure for a disease spreading on Ilus.

Avasarala faces fallout for the UN's military mission; Drummer and Ashford make big decisions about their futures within the OPA; a spreading illness on Ilus takes a toll on Amos.

Miller and Holden race to save Ilus; Murtry puts his endgame into motion, putting the Roci crew's lives at risk.

Ashford closes in on an enemy while uncovering a dangerous plot; Avasarala faces a crossroads in her political and personal lives; the Roci crew works to reestablish life on Ilus.

Holden pleads with Fred Johnson to destroy the last sample of protomolecule; Naomi gets an important lead to her son; on Luna, Avasarala hunts for Marco Inaros.

Holden and Fred deal with infiltrators on Tycho; Drummer's past comes back to haunt her; Amos returns to Baltimore.

Naomi comes face to face with Filip; Holden and Fred turn the tables; Avasarala closes in on Marco's plot.

Marco's grand plan shocks Earth, Mars and the Belt.

Amos and Clarissa are trapped in a collapsed building; Naomi contends with her old family; Holden assembles a new crew on the Roci; Alex and Bobbie make a dangerous discovery in the Belt.

Holden and the Roci go on the hunt; Amos and Clarissa seek shelter on a devastated Earth; Bobbie and Alex fight a desperate battle; Marco makes Drummer an offer she can't refuse; Avasarala returns to a position of power.