Bobbie Draper and other Martian marines undergoing combat training on Mars. They are deployed to Phoebe Research Station, which had been reported as being attacked. The United Nations debates blockading Martian fleet deployments; Avasarala backs the measure but privately believes that she is being prepared by Errinwright as a scapegoat, and hires private security. A Martian naval vessel fires on a UN vessel; the UN elects not to fire back, figuring that the Martian missiles were saber-rattling. The missiles pass the UN vessel and destroy Phoebe Station. Draper believes that war with Earth is good; her commanding officer, Sutton, believes war must be avoided. Holden and Miller recover from radiation sickness; Miller and Amos have a unhappy disagreement that is broken up by Naomi. Naomi and Holden perform repairs to the Rocinante and decide to deepen their relationship. Alex cooks lasagna for the crew of the Roci, and over dinner tensions are eased.
Arrival at Tycho Station is tense, but the Rocinante crew defuses the situation by explaining what is going on at Eros and where the data is going. Fred Johnson pulls together a strike team from rival Outer Planets Alliance factions, killing one of their leaders in the process. Rocinante is assigned as the mission's muscle, engaging the station's defenses and clearing a path for the boarding party. The station is not prepared to defend itself, and falls easily to the team. Capturing the lead scientist on the project, the man is uninterested in who he answers to as long as he can continue his work. While explaining the source, dangers, and possibilities of the Protomolecule, he is shot in the head by Miller.
Earth destroys Mars' moon Deimos in response to the MCRN's nuking of Phoebe. This creates tensions in Bobbie Draper's squad. Holden and his crew return to Tycho Station, angry at Miller for killing the lead scientist on the Protomolecule project. Fred Johnson offers Miller safe passage off Tycho, but Miller's investigations show that action must be taken against Eros. Johnson and Holden reach the same conclusion when Amos figures out how to get one of their prisoners to talk. Miller realizes that Eros must be destroyed, and that Fred Johnson has the equipment necessary to do so.
Avasarala gathers information linking the Protomolecule to Julie Mao's father. Miller's plan is put into action. After assembling a demolition team and procuring the Rocinante's services for cover, the Nauvoo is evacuated of its people and commandeered. After flying to Eros, Rocinante drops its cargo of bombs and the demolition team spacewalks to them for precise placement. A complication arises when a group of doctors is found who will not follow Holden's orders, so he destroys their ship. The debris damages one of Miller's bombs, and he chooses to stay with it on Eros, watching the Nauvoo approach and no collision take place. Holden and crew confirm that the Nauvoo did not miss - Eros maneuvered to avoid the impact.
The Rocinante chases an asteroid as it hurtles towards Earth.
Earth and Mars search for answers in the aftermath of the asteroid collision.
Preparations for the Earth/Mars peace conference tighten the tension on Erringwright.
Naomi tracks down signs of the protomolecule; Fred Johnson's control over the OPA collapses.
Bobbie becomes a political pawn in the struggle between Earth and Mars.
Holden leads his crew through the war-torn station on Ganymede. Meanwhile Bobbie makes a decision that changes her life forever.
Bobbie makes a decision that changes her life forever.
A discovery pushes Naomi and Holden apart and sets the Roci crew against each other.
The Roci crew must fight to save the ship.