Miller and the crew of the Rocinante regroup after their escape from Eros. En route to Phoebe Station, Martian Marine Gunnery Sergeant Bobbie Draper and her platoon find themselves in the middle of Earth and Mars' escalating conflict.
After learning the truth about Eros Station Fred Johnson rallies the Belter factions to join the Rocinante crew for a dangerous raid to acquire intel on the protomolecule. While political forces on Earth try to push the planet into a war with Mars, Avasarala decides to work her own back channels to get answers.
The crew returns to Tycho Station following their raid, where Miller finds himself on the outs with Holden and Amos tries to make a prisoner talk. Fred Johnson receives a desperate communique from Earth, and Mars considers its next move after Earth strikes at the moon Deimos.
Holden and the crew of the Rocinante reluctantly agree to help Miller and a demolition team from Tycho take out Eros and the protomolecule experiment once and for all. On Earth, Chrisjen confronts Jules-Pierre Mao after she discovers that his company is connected to the secret stealth ship.
With Eros on a collision course with Earth, the Roci crew chases the asteroid in the hopes of averting a catastrophe -- and Earth's government is forced to place its trust in uncertain hands. Meanwhile Miller infiltrates the station with his weapon in tow, only to find something astonishing at its alien heart.
The crew receives a hero's welcome back on Tycho Station, where Fred admits he has new plans to strengthen the OPA's position against the Inners. While Holden argues that they should destroy their surviving protomolecule sample, Bobbie Draper find more than they expected from a routine patrol.
Bobbie struggles to recover following the incident on Ganymede, which Earth and Mars blame on each other. The U.N. calls for peace talks on Earth, but when Anderson Dawes arrives on Tycho Holden and Johnson find it difficult to hold the Belters' loyalty.
In the wake of the catastrophe on Ganymede a surviving botanist finds himself on a refugee ship, with little hope that his daughter survived the attack. Fred Johnson loses his tenuous control of the OPA as Dawes' followers stage a hostile takeover of Tycho Station, and Naomi discovers signs of more protomolecule.
Bobbie arrives with the MCR contingent on Earth, where both sides hope to avoid a shooting war following the incident on Ganymede. As a UNN science vessel arrives in Venus orbit, Holden's crew hijacks a relief supply vessel in order to sneak onto Ganymede Station.
Holden's crew searches the war-torn station on Ganymede in search of a scientist connected to the protomolecule experiments, while Prax hopes for a sign that his daughter is still alive. On Earth Bobbie attempts to escape from the MCR's watchful eye, and Errinwright comes clean to Cristjen his connection to Jules-Pierre Mao.
The search for Dr. Strickland and Mei leads to a disturbing discovery on Ganymede, while on Venus the UN research team sees what Eros has left behind. Avasarala makes contact with Jules-Pierre Mao, and Bobbie confronts Captain Martens about the real reason her team was killed.
Naomi and Amos try to help the Somnambulist launch with Ganymede's refugees, while Holden and the Roci hunt for the creature that escaped the lab. As Avasarala meets with Jules-Pierre Mao, Errinwright puts his own plans into motion.
The Roci crew's attempts to expel an alien invader from their ship leaves Holden's life on the line, while Avasarala and her escorts are pinned down by the enemy with no apparent way of escape. On Venus, the UN research vessel discovers the true extent of what the protomolecule can do.
