The following version of this novel was used in the creation of this study guide: Maas, Sarah J. House of Sky and Breath. Bloomsbury Publishing, 2022. Hardcover.

The Prologue opens as Sofie enters a death camp to save her younger brother, Emile. She succeeds, passing it off to her lover Agent Silverbow, before she sacrifices herself to let them escape. An Asteri soldier- called the Hind - kills Sofie after confirming that she did not tell anyone her unknown intel.

In Part I: The Chasm, Bryce Quinlan and her boyfriend Hunt are trying to live a normal life after a deadly spring attack months prior. It is revealed that both of them killed an Archangel, but the god-like leaders of the world - called the Asteri - decided against executing them after Bryce saved the city. However, both of them suffer significant trauma and have decided to refrain from intimacy until the Winter Solstice while they try to figure things out.

However, things take a turn for the worse when Bryce’s Fae cousin Cormac announces that her father, The Autumn King, has decreed their betrothal. This angers her brother Ruhn who is also betrothed to a woman who does not love him. As they debate how to get out of the marriage, Bryce’s werewolf friend Ithan is found almost dead in her house after being beaten for defending her.

At the same time, Tharion is sent on a search for Sofie by the River Queen. He locates the blocks she was drowned with, but sees that the chains are broken. Later, he learns that her brother, Emile, escaped from the rebels, though Tharion is not certain if he is alive.

Meanwhile, Hunt is wary of his new boss, Celestina, especially when he learns that two of his worst enemies - Pollux and Baxian - have joined their squad. Celestina apologizes for the pain that Hunt suffered under Sandrial and asks him to show Baxian around, despite their differences.

This becomes more complicated when Tharion approaches Bryce for information on Sofie because her best friend Danika, who died just before the spring attack, exchanged emails with Sofie. Then, the group learns that Cormac is actually Agent Silverbow and is trying to find Emile before the radical rebel Pippa uses him as a weapon to destroy the Vanir. After a variety of conversations and a run-in with the Princes of Hel, Bryce convinces the others to help Cormac, as she wants to rescue Emile and learn the truth about Danika.

Part II: The Abyss continues as Bryce and Hunt go to the Bone Quarter to confront the Underworld King. There, They learned that the eternal, peaceful afterlife is a lie. Instead, the dead are eventually transposed into secondlight to fuel the world. This horrifies Bryce as she and Hunt combine their powers to escape the Underworld King's demons.

Meanwhile, Daybright tells Ruhn when the rebels should attack a train carrying dangerous Asteri weapons. He passes this information to Cormac, but things get more difficult as the dangerous Hind and murderous Mordoc arrive in the city with their dreadwolves.

After everyone regroups, Hunt attends the celebration for Celestina's mating ceremony. However, when Sabine attacks Bryce for harboring Ithan, Hunt rushes home to save her, disappointing Celestina who demands he stay in the barracks as punishment.

Later, Bryce, Ithan, and Tharion visit the mystics, or people the Astronomer uses to mentally search the world in exchange for their freedom and payments to their families. They meet Thanatos who confirms that Connor is still in the Bone Quarter but he has no knowledge of Emile.

Another week goes by and Bryce learns that Danika was researching forgotten wolf lineage. Cormac learns the rebels successfully attacked the spine and the group goes to Ydra. There, they learn the mechs are more deadly than before and Pippa is thrilled to wipe out the Vanir. Hunt destroys the weapons, but the group is cut off by the Hind. Then, they are saved by Sendes, commander of an underwater city ship.

Once safe, Hunt and Bryce learn that they are true mates and inadvertently share magic through intimacy. Then, the group learns Sofie is truly dead and Cormac vows to save Emile.

At the same time, Ithan meets an unnamed wolf mystic and searches for a way to save her. This causes him to steal the Astronomer's fire sprites where he learns one of them is an enslaved dragon named Ariadne.

Part III: The Pit begins as Hunt confirms that the Hind has not told anyone what happened near the island. Then, Bryce reveals that she already promised the Viper Queen a favor for harboring Emile, and he does not have any actual powers. Instead, she gets documents forged so Emile can be adopted by Ember and Randall.

Then, as Hunt and Bryce investigate what Hel might be planning, Queen Hypaxia asks Ruhn to give her a royal guard to protect her from her coven. Ruhn agrees and prompts Ithan to the task. However, Daybright warns him that Pippa may be planning to attack Crescent City and Ithan is attacked by a deathstalker when Hypaxia and Bryce meet to talk. He is badly hurt, but the women are able to stop the demon and Hypaxia heals Ithan.

A week later, everyone meets at the ball and Bryce announces her and Hunt’s relationship so that the Autumn King is forced to acknowledge it. They also learn about Hypaxia and Celestina’s illicit relationship, but all agree to work together and keep it a secret.

Meanwhile, Ruhn plans to meet Daybright in person, but decides against it when he sees both the Harpy and the Hind waiting. He later apologizes for putting her in danger, but admits that he hopes she is not as cruel as them.

After Apollion tells Bryce that the Fae were allies of the Princes of Hel, the others consider what they may have to game. Bryce is forced to placate Cormac who is furious at her for lying to him, but he calms down once she promises that Emile is safe. Unfortunately, things get worse when Hypaxia and Ithan come back from a trap set by the Under-King during their attempts to speak to Connor and say that Bryce must go to Urd’s Temple or Connor will be turned into secondlight immediately.

Bryce, Hunt, Hypaxia, and Ruhn meet the Under-King in Urd’s Temple and learn that he set them up to be killed by Pippa. Bryce is able to get Hypaxia and Ruhn out while baiting the Asteri forces to attack the rebels. Baixian arrives to save her and Hunt, revealing that he was Danika’s mate. Before she died, she was obsessed with learning what was in a room in the Eternal City.

Declan later confirms that Sofie did find the room, though she left with nothing but a horrified expression. The group decides they have to break into the archives and clear up any concerns they have before leaving. This leads to Ithan learning that the wolf mystic is likely a lost heir that can challenge Sabine. Tharion dedicates himself to the Viper Queen to escape certain imprisonment by the River Queen.

Meanwhile, Ruhn sleeps with Daybright in their mindscape, but panics when she is pulled away from him while shouting about the dungeon. When he convinces Bryce to help rescue her, the group decides that Cormac and Tharion will bait Pippa into attacking the lab and then they will blow everything else.

As Cormac sacrifices himself to stop Pippa, Bryce learns that the Asteri are actually parasites who have conquered many worlds and use the energy of their victims to sustain themselves. However, Rigelus confirms that they are trapped in Midgard by Bryce’s Fae ancestors and he intends to use her to reopen the gates and enact his revenge.

After it is revealed that the Hind is Daybright, she leaves Bryce’s shackles open as she and Pollux take Bryce, Hunt, and Ruhn to the Asteri. Bryce is able to free Hunt and Ruhn and escape through the portal. However, while the Hind’s double agent nature is not revealed, Ruhn, Hunt, and Baxian are left behind and Rigelus brands Hunt with a new slave mark.

Meanwhile, Bryce wakes up in a new world and meets a group of Fae led by a man named Rhysand.

In the Epilogue, Ithan learns what happened in the Eternal City. He begs the wolf mystic to wake up and help him save his pack, which she does as the book ends.