Following the events of Tiamat's Wrath, Winston Duarte, seemingly awakening from his semi-catatonic state, projects himself into the mind of Admiral Trejo, who is currently reconquering the Sol system for the Laconian Empire. Duarte expresses gratitude for Trejo's efforts in preserving the Empire and admits they had been thinking too small in their empire-building vision. Duarte then vanishes, prompting Trejo to order a return to Laconia. Upon arrival, Duarte has already disappeared from the state building, and Colonel Aliana Tanaka is tasked to locate him with the highest level of clearance.

Tanaka's search leads her to the cave Amos Burton once inhabited, where she deduces that Duarte likely left in an alien ship. She decides to use Teresa as bait to lure Duarte and begins investigating a girls' boarding school on a colony world as a possible location for Teresa. Meanwhile, Elvi and her team, along with the immortal children Xan and Cara, are investigating the Adro Diamond. As they dive into the library using the catalyst, some of Cara's experiences bleed into Amos, who has been similarly altered.

The Rocinante crew (Jim, Naomi, Alex, Amos, and Teresa) are avoiding Laconian ships while Naomi manages the underground resistance. They transit to New Egypt to take Teresa to the boarding school, where they encounter Tanaka and Laconian marines. After a firefight, they escape to the Rocinante and flee to the Freehold system, a safe haven. However, Laconian forces are present, suspicious of the ship and alert Tanaka. As the Rocinante covertly resupplies at Draper Station, Tanaka arrives in the system and delivers a message from Trejo to Naomi. The message offers an armistice and alliance between the Laconian Empire and the underground in exchange for implementing Naomi's gate travel protocols, withdrawing Laconian forces, and returning Teresa. The crew deems Trejo's demands unreasonable, but Jillian Houston takes matters into her own hands, locking the Rocinante crew in their quarters and accepting the Laconian offer. Tanaka, however, has no intention of honoring the deal and kills Jillian's guards before searching the station for Teresa.

Jillian releases the Rocinante crew, who launch and escape through the ring gate, while the Gathering Storm sacrifices itself to cover their retreat. Amos convinces the crew to head to the Adro system to meet Elvi and aid in the investigation of the diamond. Tanaka, losing the Rocinante's trail, mistakenly follows another ship to the Bara Gaon system. During their search, a large ship enters the ring space from the Sol system, seemingly about to be annihilated, but it miraculously survives. This event causes the rings to glow brightly and triggers a shared memory experience among those in the ring space and aboard the ship.

The mysterious "dark gods" or "ring entities" have been attempting to kill humans in various ways, with limited success. However, one event eradicates all but the most basic life forms in one system. When the Rocinante finally reaches the Adro system, they decide to perform a dual dive into the library with Cara and Amos. During this process, Duarte appears, proposing that humanity must join him in creating a hive mind to counter the ring entities' attacks.

Following the dual dive, Amos convinces Elvi to cease the dives with Cara for ethical reasons. Meanwhile, Tanaka, troubled by the shared memory experience, seeks psychiatric help and receives medication to mitigate the issue. She learns that Laconian scientists believe they have found Duarte's egg ship on the surface of the Ring Station, and both the Rocinante crew and Tanaka decide to head there. Naomi sends Trejo a message accepting his offer and providing the data from the dual dive experiment, while simultaneously sharing the information with the underground resistance and urging them to send ships to the Ring Space. Trejo orders Tanaka to either retrieve Duarte or assume control.

Upon arrival in the slow zone, Tanaka, Teresa, and Amos perform a dive that displeases Duarte. Jim injects himself with protomolecule to reconnect with Miller and the ring station, joining Tanaka and Teresa in the search for Duarte. As more ships arrive, some lose contact as Duarte gains control of their crews through his burgeoning hive mind. Inside the ring station, the team finds Duarte connected to the station, creating his hive mind and stalling the dark gods.

Teresa's attempts to free Duarte fail, and Tanaka kills him, simultaneously ending the hive mind and unleashing the dark gods on humanity. In the ensuing struggle, Tanaka is also killed. Jim connects himself to the station and holds the dark gods at bay while Teresa escapes and the remaining ships exit the slow zone. Once the slow zone is empty, Jim destroys the ring station, severing the dark gods' connection to the human universe and causing the ring gates to collapse and fall towards their local stars. The 1,300 colony systems are left to fend for themselves.

In an epilogue set 1,000 years later, a team from The Thirty Worlds, a federation of 30 colony worlds, journeys to Earth utilizing human-designed faster-than-light travel, where they are greeted by Amos Burton.

• Official website