Unlikely allies Joe Miller and the crew of the Rocinante led by Jim Holden uncover more about the conspiracy to release the protomolecule on Eros station.

With the help of Fred Johnson and the OPA, Miller, Holden and the crew stage a raid for information on the protomolecule. On Earth, Avasarala learns a truth about Fred Johnson.

The Rocinante crew deals with the fallout over Naomi's betrayal while caught in the middle of the war between Earth and Mars while Avasarala and Bobbie hatch an escape plan.

The Rocinante answers an unexpected distress signal. Bobbie and Avasarala find themselves being hunted by a mysterious captor. UN Secretary-General Sorrento-Gillis brings in a colleague from his past to lend an ear during this crucial time of war.

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.

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.

Holden and Miller 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 personal and political life. The Roci crew works to reestablish life on Ilus in the wake of a deadly catastrophe.

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.

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.

The Rocinante crew make a startling discovery on an asteroid. Avasarala and Bobbie contend with the devastation on Earth. Drummer and her family must make a heartbreaking decision. On Ceres, Marco and Filip's struggles turn inward.

In the thrilling season finale, Inners and Belters fight side by side with the crew of the Rocinante in a last, massive, desperate battle with Marco and his Free Navy, with the fate of the Solar System, the Ring Gates, and of all humanity hanging in the balance.