In the wake of the disaster on Eros, the crew of the Rocinante is forced to regroup and recuperate ... including Joe Miller, who's been brought into the fold. The Roci crew is a bit traumatized by what they saw on Eros, and they vow to hide the piece of the protomolecule they took amid an asteroid field until they know what to do with it.

After returning to Tycho station, the Roci crew and Fred Johnson come up with a plan to overtake the research station where the data from the Eros experiment was being beamed. Once there, they unhook one scientist, the emotion-less Cortazar, from a neural network and come upon Dresden, the man who was overseeing the abomination on Eros. Fred wants to bring him back to Tycho, but Miller instead shoots him dead.
 

With Eros still teeming with protomolecule activity, Fred and Miller come up with a plan to knock Eros on a course into the sun by ramming the Mormon ship Nauvoo into it. The plan appears to be working perfectly — until Miller ends up stuck on Eros while trying to set charges. The collision with the Nauvoo never happens, though, because Eros, powered by the protomolecule, moves out of the way.

Miller is still stuck on Eros, though, so he's able get inside, through corridors thick with protomolecule, and gets to the center, where Julie Mao is being animated by the protomolecule. It's she who is controlling Eros' course. Miller has a sweet, sad last moment with Julie, as he convinces her that she has to change course. He's successful, and Eros, Miller, and Julie all crash into the surface of Venus instead, saving Earth and (one assumes) killing Miller in the process.

While Avasarala struggles to keep Earth and Mars from armed conflict in the wake of the Ganymeade attack, Bobbie must cope with the news of her dead team. She tells Martian officials about what she saw — a drone overhead just before the attack, and of course the figure without a space suit, which she realizes was chasing the UN forces which made Bobbie's team think they were attacking. But she's told there's no evidence of this She's to attend the Earth/Mars summit in New York and testify (falsely) that her team fired first in order to prevent a Earth/Mars war. 

One survivor of Ganymede is Dr. Praxidike Meng, a botanist who fears his daughter — who was off at a doctor's appointment at the time of the attack — has been killed. After Prax is witness to the belters on his rescue ship blowing Martian survivors out of an air lock, he's traumatized. He ends up on Tycho station, which is a coincidence, since ...

In order to get onto Ganymede, the Rocinante crew commandeer the relief ship the Weeping Somnambulist. They're able to get to Ganymede, but in an ensuing shootout with gangsters on the ground, the husband of the Somnambulist's captain is murdered. Naomi is badly shaken up by this.

Bobbie is then dragged back to the Martian embassy, where she's told that she's never going to be a soldier again AND learns her unit was knowingly sacrificed to test the rotomolecule hybrid. After Bobbie escapes again, she makes a run for the Earther guard post and declares that she's seeking political asylum.

After the shootout, Naomi tells Holden she can't keep going down the path they're going. She re-joins the Somnambulist and tries to evacuate the remaining Ganymede survivors. There are too many to fit on the small relief ship, though, and she has to struggle to convince the belters to not riot as they board.

Holden and Naomi are reunited aboard the Rocinante, and Holden's mania has subsided some. Only now the hybrid has gotten aboard the Roci, and our crew needs to kill it before it kills them. Holden almost dies as the attempt to overtake the creature. The only solution is to lure it outside of the ship with a nuclear missile and then roast it. Which they do.

Meanwhile, the research ship that Earth had sent to get data readings from the Eros crater on Venus attempts to drop closer to the surface — since other readings near the crater have proved impossible. Just as the ship approaches the crater, it is pulled apart by the protomolecule, which seems to have survived its crash landing on Venus just fine.