Miller, Holden and the crew of the Rocinante deal with the aftermath of their narrow escape from Eros. We meet Martian Marine Gunnery Sergeant Bobbie Draper and her platoon when the "Cuban Missile Crisis" between Earth and Mars heats up.

With the aid of Fred Johnson and OPA fighters, Miller, Holden, and the crew of the Rocinante stage a dangerous raid in search of information about the mysterious Protomolecule. On Earth, Avasarala learns an important truth about Fred Johnson.

Returning to Tycho Station, Holden and Miller butt heads about how the raid was handled. Meanwhile, Naomi and Alex deal in different ways with the post-traumatic stress of the incident. Holden and Amos interrogate an affectless scientist. Avasarala reaches out to an enemy to forge an unlikely alliance.

Miller devises a desperate and dangerous plan that includes stealing the massive Mormon generation ship, the Nauvoo, to eradicate what's left of the Protomolecule on Eros; and Holden, the Rocinante crew, and Fred reluctantly agree. Meanwhile, Avasarala discovers who is behind the Protomolecule project.

It's a race against time as the Rocinante chases an asteroid, now hurtling toward Earth. As Earth prepares for the worst, Avasarala is surprised to learn Holden is still alive and that the Rocinante may be Earth's only hope of averting a cataclysmic disaster.

Earth and Mars search for answers in the aftermath of the asteroid collision and Avasarala wages war against Jules-Pierre Mao. The Rocinante crew continue their quest of eradicating the Protomolecule. Naomi and Holden's differences in opinion cause Naomi to take actions into her own hands. Bobbie and her Martian fire team arrive on Ganymede patrol and are faced with the unthinkable.

The preparations for an Earth/Mars peace conference tightens the tension on Errinwright. Bobbie's debriefing uncovers a deeper mystery after the attack on Ganymede. Anderson Dawes uses the flow of refugees coming into Tycho for his own ends, threatening to destabilize the uneasy alliance between Fred Johnson and Holden.

As Naomi tracks down signs of the Protomolecule in unexpected corners of the solar system, Fred Johnson's control over the OPA begins to collapse. A traumatized refugee from Ganymede may hold the key to finding a new threat.

Holden crosses his own ethical boundaries in order to sneak into the war zone on his hunt for the Protomolecule and the people behind it. Bobbie becomes a pawn in the political struggle between Earth and Mars, but Avasarala recognizes her chance to expose the enemies of humanity on both sides of the negotiation.

Holden leads his crew through the war-torn and failing station on Ganymede. Errinwright and Avasarala have a confrontation that changes their relationship forever, and Bobbie discovers a side of Earth that shakes her basic understanding of her enemy.

The Rocinante crew make a gruesome discovery, unleashing something they can't comprehend. Bobbie makes a decision that changes her future and remakes her past, while Avasarala finally makes contact with the elusive Jules-Pierre Mao.

A horrible discovery in a secret lab pushes Naomi and Holden apart and sets the crew of the Rocinante against each other. Avasarala and Bobbie make a dangerous rendezvous with the fate of humanity in the balance, and a result that no one on either side could anticipate.

The relief of the Rocinante's narrow escape is shattered by an unexpected enemy and the crew is forced to fight to save the ship. Avasarala is trapped by enemies and far from help, Bobbie Draper is her only chance to survive.