All eyes turn to the edge of the solar system as a mysterious new presence emerges; Naomi recommits to her roots; Drummer butts heads with a seasoned new commander aboard the Behemoth; and a young Belter makes a name for himself.

An old friend taunts Holden with the answers he seeks. Naomi struggles to fit in. A mysterious low-level tech aboard the Thomas Prince enacts a terrifying plan.

The Rocinante seeks a new gameplan as they attempt to avoid capture. Melba's true motives are revealed. Naomi is torn between identity and ideal. Anna seeks a way to stay aboard the Thomas Prince.

As survivors arrive to the Behemoth, two factions form over how to handle a life-or-death threat. Holden grapples with what he's seen and the choices he must make.

Holden and his allies must stop Ashford and his team from destroying the Ring, and perhaps all of humanity.

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.

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.

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.

With an unexpected passenger aboard the Rocinante, Holden and crew undertake a dangerous mission that could shift the balance of power in the war. Drummer decides to make an uneasy alliance. Filip wrestles with his guilt.

Avasarala, with the Combined Fleet of Earth and Mars, takes the war to Marco. Filip and Marco's relationship is tested. The war becomes more perilous and personal for Holden and Naomi when the Rocinante is suddenly forced into a battle.

Holden finds himself at odds with his crew when a controversial decision is uncovered. On Ceres, Avasarala struggles to contain an escalating humanitarian crisis. Drummer's growing faction stage a daring raid with dire stakes. Filip, demoted to repair skiff duty, makes an unexpected discovery.

Paths converge on Ceres when Drummer and her fleet arrive to aid the relief effort. Holden tries to convince Avasarala to release crucial information that might avert catastrophe, but she has her own request of him. As Amos and Bobbie get a little R&R at the station, Naomi has a difficult and long-awaited reunion.

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.