Calibans War
by James S. A. Corey
On Ganymede, Mei Meng is kidnapped from her preschool by her doctor. Several hours later, Earth and Martian space marines are attacked and effortlessly killed by a super soldier, with Bobbie Draper, a Martian marine, the only survivor. Earth and Mars begin a shooting war which throws Ganymede into chaos. In the aftermath, Mei's father Praxidike Meng fruitlessly searches for his daughter in the midst of the societal breakdown in the Ganymede colony.
Several months later, the crew of the Rocinante are tasked with delivering emergency aid to Ganymede. Meng spots James Holden during a food riot and asks the crew to help find his daughter. They agree and are able to trace her kidnappers to unused tunnels on the moon. Holden, Meng, and ship mechanic Amos Burton discover a secret lab. In the midst of a shootout with lab security, they inadvertently release another super soldier who kills some of the lab personnel. In the wake of the battle, the crew find remnants of the protomolecule and the corpse of Mei's friend, who was being treated by Mei's doctor for immunodeficiency. The crew rush to escape the station as more chaos erupts around them, and are able to make it back aboard the Rocinante.
Draper is brought to the peace talks between Earth and Mars occurring on Earth, giving testimony regarding the super soldier attack on Ganymede. She violates diplomatic protocol and is dismissed by the Martian delegation, but is then hired by Chrisjen Avasarala, who is leading the UN negotiations. Draper discovers that Avasarala's assistant is betraying her, leading Avasarala to conclude that her UN superiors are trying to get rid of her, from which she deduces that a group within the UN is responsible for the super soldier attack. Avasarala allows Draper to be brought along as her bodyguard on a slow-moving yacht headed to Ganymede on an ostensible relief mission.
On their way to Tycho station, the Rocinante crew discovers a super soldier stowed away in their cargo hold. They are able to lure out the creature using radioactive bait before vaporizing it with the ship's exhaust. The Rocinante is damaged during the encounter, but the crew learn more about the super soldiers. Holden confronts Fred Johnson, who he believes controls the only other sample of the protomolecule. Johnson denies involvement with the Ganymede incident and fires Holden's crew. They help Meng release a video asking for help searching for Mei, raising enough money to continue the search. Upon receiving information about Mei's doctor, Meng deduces that the super soldiers are being created on a base on Io. With the Rocinante repaired, they set out to recover Mei.
On board the yacht, Avasarala sees Meng's video appeal and learns that a UN detachment is heading to intercept the Rocinante. The crew of the yacht prevent her from warning Holden, claiming that their communication systems are broken. When they refuse her demands to get the yacht repaired, Avasarala has Draper take control of the vessel. Avasarala sends a warning to Holden, and she and Draper board a racing pinnace to rendezvous with the Rocinante. After meeting Holden's crew, Avasarala and Draper share notes of the super soldiers. Realizing that they are several days away from being destroyed by the UN detachment, Avasarala convinces the crew to let her send this information to her contacts within the UN to prevent an all-out war.
Draper and Avasarala convince the Martian fleet to help protect the Rocinante. This culminates in a space battle between the UN detachment, the Martian forces, and a second UN fleet loyal to Avasarala. With the UN Secretary General recalling the admiral hostile to the Rocinante, the battle ends in victory for the Martians and Avasarala's faction. The crew lands on Io, where Amos and Meng rescue Mei along with other immunodeficient children. Draper kills a super soldier using knowledge about its capabilities. The crew heads back to Luna, where the people responsible for the super soldier project are brought to justice. Avasarala is promoted, Meng is hired to oversee efforts to restore Ganymede, Draper returns to Mars, and the Rocinante takes a contract escorting a supply ship. Throughout the story, the solar system had been watching changes on Venus, which culminate with the launch of something unknown as the book ends.