As Chrisjen struggles to keep herself and her people alive, Errinwright moves to press Earth into a war declaration. The Rocinante crew reckons with the fallout of Naomi's betrayal, and Fred Johnson returns to Tycho Station with his prize.

Pursued by a U.N. ship, Draper and Avasarala are forced to send up a distress flare -- and the Roci crew debate whether or not to respond. U.N. Secretary General Esteban Sorrento-Gillis recruits an old friend, Rev. Dr. Anna Volovodov, to help sell the war to his people.

As Avasarala and Bobbie find refuge among a conflicted crew, Earth considers a first-strike against Mars' network of spy satellites. The U.N.N. Agatha King picks up survivors from Mao's ship, and Anna pushes Sorrento-Gillis to weigh the mortal cost of his decisions.

The Rocinante enters the debris field of an old battle to scrounge for fuel and supplies, only to find Martian soldiers still alive. As the Sec-Gen addresses the U.N. General Assembly, Avasarala struggles to find a way to get her message out.

Earth and Mars stand on the brink of a shooting war when their fleets meet near Io, as the captain of the U.N.N. Agatha King contemplates an insurrection against Admiral Nguyen. As the Roci bears down on Mao's research facility on Io, the scientist gains new insight into the protomolecule's collective agenda.

Holden leads a team inside Prospero Station, where a new hybrid threat has been unleashed – while Alex and Naomi attempt to board the Agatha King. On Earth Anna confronts the Secretary General with Errinwright's treachery.

Six months after the emergence from Venus ships from Earth, Mars, and the Belt converge on a mysterious Ring at the outer edge of the solar system. While Holden, Alex, and Amos host a documentary film crew, Drummer has a philosophical difference with the new first officer of the O.P.A. ship Behemoth.

On the edge of the Ring Holden experiences hallucinations of Detective Miller, who taunts him with the possibility of answers – while a saboteur quietly does his work. A low-level tech on the U.N.N. Thomas Prince executes her deadly plan.

The Rocinante crew find themselves inside the Ring and running out of options, with the Martians and Belters hot on their tail. While Melba recalls what brought her to this moment, Anna looks for a way to stay on board the Thomas Prince after Avasarala orders all civilians evacuated to Titan.

With Bobbie Draper and the M.C.R.N. Marines in pursuit James Holden approaches the alien structure at the heart of the Ring, uncertain whether or not he can trust his hallucination of Miller. As the Thomas Prince enters the Ring, Melba's mission is threatened when she is recognized.

After a massive deceleration event the Earth, Mars, and Belter ships inside the Ring cope with massive losses. While Drummer and Ashfold try to survive being pinned down, Anna tends to the wounded on the Thomas Prince, and Bobbie Draper tries to keep Holden alive.

With the Behemoth taking on the wounded the Roci crew heads to the Belter ship, hoping to locate Holden. Dr. Kolvoord comes up with a plan to try and get a signal out of the ring, and Drummer fights to get back on her feat.

Ashford sets himself on modifying the Behemoth's laser transmitter to destroy the ring, as Drummer and the Rocinante crew hatch their own plan after Holden claims that he has a way to stop the alien station – pitting the two factions against one another, with the fate of the human race at stake.