Queen Makhi receives a wedding invitation from Nikolai Lantsov for his marriage to Princess Ehri, and confers with her adviser Yerwei about her failed assassination plot against both the king and her own sister. A mysterious blight of shadow sweeps over the palace grounds, killing her niece Akeni and devastating the royal orchards.
Nina Zenik, disguised as Mila Jandersdat, visits Djerholm's marketplace with Hanne and the Brum family. The Hringsa network stages a miracle involving a play about the Saints and a wave that knocks Jarl Brum off his feet. Nina steals a note from Brum's pocket revealing Fjerda is preparing to march to war, and resolves to get the intelligence to her king.
Nikolai rides out with Zoya, Tolya, and Tamar to survey a new occurrence of the blight near Yaryenosh. They intervene to protect a Suli encampment from a hostile mob, and then receive Nina's urgent message warning that Fjerda is on the march, sending them racing to prepare for war.
Nina and Hanne are woken by the arrival of a new Wellmother from the convent at Gafvalle, who confronts the Brums about contraband found in Hanne's former quarters. Hanne admits to the riding clothes but denies the religious items, and the family narrowly avoids exposure. The chapter ends with a shocking twist when the Wellmother addresses Nina by her real name, revealing herself as a Grisha spy.
Zoya meets with Kerch delegate Hiram Schenck in Os Kervo alongside Count Kirigin, but the Kerch refuse to aid Ravka. She experiences disturbing sensory episodes from the dragon within her. Afterward, two assassins attack her on the docks, and though she kills one and captures the other, she discovers they are followers of the Apparat who call her Sankta Zoya.
Nikolai leads Ravkan forces at the Battle of Nezkii, where Nina's intelligence allows them to plant anti-tank mines and prepare an ambush. Zemeni airships arrive with the parem antidote, freeing Fjerda's drugged Grisha prisoners and turning the tide. Adrik and Nadia command the Squallers while Nikolai meets with Zemeni commander Kalem Kerko.
The Wellmother reveals herself as a Ravkan spy planted by Tamar, and delivers a new mission from Nikolai: find Queen Tatiana's letters and get close to Vadik Demidov. Nina and Hanne devise a plan for Hanne to enter Heartwood, the Fjerdan marriage season, to gain access to the Fjerdan court and its secrets.
Nikolai returns to Os Alta to find Princess Ehri and her Tavgharad have attempted an escape. The Tavgharad set themselves ablaze on the palace steps in a suicide mission ordered by Queen Makhi, nearly killing Ehri. Nikolai is burned trying to save the princess, and Zoya extinguishes the flames, but all eleven Tavgharad guards perish.
Zoya tends to Nikolai as a Healer treats his burns, then joins Genya, David, Nadia, Tamar, and Tolya in her sitting room. They discuss Queen Makhi's motives. Then Zoya and Nikolai visit the Darkling in his glass prison, where he offers to reveal how to stop the expanding Fold in exchange for a visit from Alina Starkov.
At the Heartwood processional, Prince Rasmus collapses coughing blood while greeting Hanne, who instinctively uses her Grisha healing power to save him. Nina and Hanne are summoned to the prince's private chambers, where Nina is separately brought before Queen Agathe and uses her power over the dead to leverage the queen's secret - that she once used a Grisha Healer to carry her son to term.
Zoya and Nikolai discuss the Darkling's demand. Nikolai reveals he can now separate the demon from his body and control it. Zoya plans to escort the Darkling to meet Alina at an abandoned sanatorium, while Nikolai stays behind for the wedding. She consults with Genya and David about the obisbaya and the thorn wood, and says a private farewell to Nikolai.
Nikolai visits the recovering Princess Ehri and brings Mayu Kir-Kaat to help convince Ehri of her sister's treachery. He then accidentally flies into a rocket test at Lazlayon and is nearly killed, saved only by Nadia and Adrik's Squaller power. At the laboratory, David refuses to build city-killing weapons, and Leoni reports on the titanium shortage.
Nina cultivates her relationship with Prince Rasmus and Queen Agathe while Hanne secretly heals the prince. At a court salon, Nina meets Vadik Demidov and the Apparat, and learns the letters are kept in the heavily guarded druskelle sector. She and Hanne begin planning a break-in during the upcoming royal hunt.
Zoya transports the shackled Darkling to meet Alina at the sanatorium. Alina Starkov arrives with Mal Oretsev and Misha. The Darkling and Alina have a tense exchange, but it is all a ruse - the Darkling uses a hidden piece of thorn wood to pierce Alina's and Mal's hands, reclaiming his shadow powers and escaping on nichevo'ya as Zoya fights helplessly.
On the morning of the 'royal wedding,' Nikolai surprises Queen Makhi by staging David and Genya's wedding instead of his own. He reveals that Ehri has been sent home to Shu Han with Tamar and Mayu to expose Makhi's treachery. Nikolai forces the queen to sign a treaty guaranteeing peace and Grisha rights, while his demon nearly breaks free as the Darkling escapes far away.
During the royal hunt, Nina manipulates Queen Agathe by hinting at Djel's displeasure with war, then uses a Hringsa-staged distraction to get Brum to take her and Hanne into the druskelle sector. She sneaks into Brum's office and uses acid to destroy the letters in his safe, but discovers a hidden prisoner - Magnus Opjer, Nikolai's true biological father, kidnapped to authenticate the letters.
Zoya witnesses the Darkling's escape from the sanatorium, where he summons nichevo'ya shadow soldiers and flees after being shot by overhead flyers. Alina and Mal refuse to evacuate Keramzin despite the danger, and Alina encourages Zoya not to give up, insisting the Darkling can be beaten and that he fears what Zoya might become.
After Queen Makhi departs and the treaty is signed, Nikolai celebrates with Genya and Tolya. Late that night, Fjerdan bombers attack Os Alta, striking the Grand Palace and the Little Palace. Nikolai takes to the skies in his flyer and releases his demon to hunt the enemy aircraft. He returns to find the Materialki workshops destroyed and Genya on her knees in the rubble, unable to find David.