The Mercy of Gods (2024) is the first book in a space opera trilogy called The Captive’s War by James S. A. Corey, a pseudonym for collaborators Daniel Abraham and Ty Franck, best known for their series The Expanse.

The Mercy of Gods follows Dafyd Alkhor and a large cast of characters who must survive imprisonment following their planet’s invasion by an alien species called the Carryx. Dafyd and his colleagues must navigate an inscrutable test on an alien world to prove their usefulness and earn the survival of their species. In prose that is at turns methodically scientific, deeply philosophical, and brutally violent, the novel examines complex issues of Colonization and Dehumanization, The Ethics of Survival, and The Human Drive to Understand.

This study guide uses the 2024 hardcover edition published by Orbit.

Content Warning: The source text and this study guide contain depictions of violence, captivity, enslavement, mental health struggles, suicidal ideation, and death.

Plot Summary

Humans appeared on the planet Anjiin 3,000 years ago. No one knows how or why they arrived there, and for centuries no one has been able to enable human genetics to communicate with the Indigenous biome. Now, Dafyd Alkhor and the other members of Tonner Freis’s research team have unlocked this genetic translation. Although Dafyd Alkhor is an assistant on the team, he’s intelligent and politically savvy. He uncovers rumors that a rival science academy plans to break up the team and take its research. He warns Else Yannin, who is the team’s second lead, Tonner’s girlfriend, and Dafyd’s unrequited crush.

Tonner, Else, Dafyd, and the rest of the team (including Jessyn, Campar, Irinna, Synnia, Nol, and Rickar) discuss the takeover. Rickar reveals that he betrayed the team in exchange for a promotion from his superior Samar Austad. However, when they find Austad dead, they halt the takeover. Before the team can recover, however, Jessyn’s brother, Jellit, and his astronomy research team announce that they have detected alien vessels heading their way. Meanwhile, unbeknownst to all, an alien spy called “the swarm” (28) has secretly infiltrated humanity by taking over human bodies as hosts. It killed Austad and now lies in wait among them.

The vessels belong to the Carryx, who have conquered hundreds of worlds, integrating those it finds useful and annihilating the rest. They’re at war with an unknown enemy, for which the swarm works. The Carryx invasion lasts five days. During the invasion, the Carryx kill Synnia’s husband, Nol, and capture Dafyd, Else, Jessyn, Synnia, and Campar, placing them aboard a transport vessel.

They travel on the vessel for weeks, during which Dafyd and Else begin an affair, and Jessyn worries about her deteriorating mental health as her medication supply runs out. On the vessel, they meet fellow captive Urrys Ostencour. He plots to overthrow their captors and recruits revenge-obsessed Synnia to his cause, but the plot fails.

The Carryx house the humans in a prison ziggurat with other aliens and place Tonner’s team—including Tonner, Irinna, and Rickar, who arrived on a different vessel—in communal quarters. Their Carryx keeper, Tkson, tasks them with conducting genetic research, ordering them to make berries from one planet edible for a creature from a different planet. The team sets to work. Dafyd and Else continue their affair; however, although Dafyd doesn’t know it, the swarm has taken over Else and has merged with the personalities of its hosts. Meanwhile, Jessyn runs out of medication and struggles with suicidal ideation.

The human team discovers that another alien species called the Night Drinkers are also working on the berries experiment. The Carryx will consider whoever succeeds first more useful to them. One day, Jessyn has an idea to replicate her medication and briefly leaves Irinna alone to do this. While she’s gone, the Night Drinkers attack the lab, destroying their equipment and killing Irinna.

The team continues working in their communal quarters for safety, but the Night Drinkers attack again, using chemical weapons. The humans fight them off. Then, replicating the chemical weapon, the humans fight and injure the Night Drinkers, who surrender and give them a translator as a peace offering.

Using the translator to question the other aliens, Dafyd finds Jellit and his astronomy research team. Meanwhile, the Carryx deem the Night Drinkers unworthy of survival because of their loss and slaughter the entire group. Jellit and his team have already found other human captives, including Urrys, who has new plans for another uprising. Urrys recruits Synnia and Jellit, among others. They intend to attack the Carryx with the chemical weapons.

Dafyd and Else object, arguing that the Carryx will destroy humanity in retaliation. Urrys and Jellit insist that it’s better to die fighting than live enslaved. The swarm tells Dafyd about the war against the Carryx, implying that Else is cooperating with the swarm (rather than being killed by it) and insisting that the uprising will harm the war effort. The swarm convinces Dafyd to betray the uprising to Tkson. Dafyd agrees to do so only if they keep Jellit safe so that Jessyn doesn’t lose her brother. The swarm agrees to convince Jellit to switch sides.

Dafyd tells Tkson about the uprising, and Jellit cooperates with him. Though Dafyd doesn’t know it, the swarm has left Else’s dead body and has taken over Jellit’s instead. The Carryx kill the resistance, leaving Tonner’s group and thousands of other humans alive. The leader of the Carryx, the Sovran, then kills Tkson and appoints a different Carryx, Ekur-Tkalal, as the new human keeper. Ekur informs the team that they have secured the safety of their species and appoints Dafyd as the advocate for humanity. Dafyd resolves to learn everything he can about the Carryx and use it to destroy them. Silently, the swarm now controlling Jellit vows to stay by Dafyd’s side and help him win the war.