Holden tries to convince Fred Johnson to destroy the last sample of protomolecule. Naomi gets an important lead to her son. On Luna, Avasarala begins to hunt for Marco Inaros.

Holden and Fred deal with infiltrators on Tycho. Drummer's past comes back to haunt her. Amos returns to Baltimore. Alex and Bobbie's investigation on Mars leads to rogue soldiers.

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.

Naomi makes a desperate attempt to save her son from Marco. On the Roci, Holden battles for the last sample of protomolecule.

Amos returns to Baltimore with Clarissa. On Luna, Avasarala's alliances begin to shift. Alone and adrift, Naomi becomes a deadly lure.

Amos, Clarissa, and a gang of thieves work together to leave Earth. Avasarala tries to head off a brutal military strike. Drummer's new family bonds are tested as Naomi's life hangs in the balance.

Holden and the Roci face off against Marco's forces and Drummer, while Alex and Bobbie attempt a dangerous rescue of Naomi, and the balance of power in the Solar System shifts.