Six of Crows

After finding that Bo Yul-Bayur is already dead, the crew instead extracts his teenage son Kuwei Yul-Bo, who has been forced to continue his father's jurda parem research. Matthias and Nina choose to spare Kuwei rather than kill him, blowing up the Ice Court lab as they flee. Reunited with Kaz and the others, the crew fights through pursuit, and when a Fjerdan force with a parem-enhanced Heartrender blocks their escape at the docks, Nina takes the drug herself to overpower them, though it leaves her badly addicted to it as they sail for Ketterdam.

Back in Ketterdam, the crew splits so Nina can begin withdrawal under Wylan's care while the rest deliver "Kuwei" to Jan Van Eck. Van Eck reveals his true motive was never protecting the world from jurda parem — he wants the formula for himself to profit from its eventual release — and he betrays the crew by sinking their ship, indifferent to the fact that Wylan is supposedly aboard. He also reveals he considers his own son unfit to inherit his merchant empire because Wylan cannot read.

Kaz then springs his own twist: the boy Van Eck has actually been given is not Kuwei at all, but Wylan, magically disguised by Nina's Tailoring ability to look like the scientist's son. The real Kuwei remains hidden with the crew. Enraged at being outmaneuvered, Van Eck kidnaps Inej and gives Kaz seven days to hand over the genuine Kuwei in exchange for her life and their promised payment.

Unwilling to risk Inej's safety, Kaz lets Van Eck walk away rather than force the issue immediately. He and the remaining crew turn to Pekka Rollins — the gang boss responsible for the death of Kaz's brother Jordie, and a man Kaz had deliberately freed from an Ice Court cell during the heist. Kaz sells off his shares in the Crow Club and the Fifth Harbour to raise the money he needs, and the book closes with him setting a plan in motion to rescue Inej and reclaim what Van Eck owes them.

As Crooked Kingdom opens, the core crew — Kaz Brekker, Inej Ghafa, Nina Zenik, Matthias Helvar, Jesper Fahey, and Wylan Van Eck — has just returned to Ketterdam from a successful but costly heist to the Ice Court in Fjerda, where they were hired by wealthy merchant Jan Van Eck to retrieve Bo Yul-Bayur, inventor of the mind-controlling drug jurda parem, and stop the formula from spreading.

At the Ice Court they learned Yul-Bayur was already dead, and instead extracted his son, Kuwei Yul-Bo, who can replicate the drug. Nina and Matthias, once enemies (Matthias a former Fjerdan Grisha-hunter who'd captured Nina, then was wrongly imprisoned because of her actions to protect him), reconciled and fell fully into an alliance and romance, with Matthias swearing a sacred vow to protect her. Escaping Fjerda, Nina was forced to take jurda parem herself to subdue a military force, and she returned to Ketterdam addicted to it and now suffering withdrawal, being cared for by Wylan.

Back home, Van Eck revealed his true agenda: he wanted the parem formula for his own profit, not to protect the world, and he betrayed the crew, sinking their ship (with, he believed, Wylan/Kuwei aboard) and disowning Wylan as an unfit heir because Wylan is illiterate. Kaz countered by revealing that the boy delivered to Van Eck was not Kuwei at all, but Wylan, disguised by Nina's Tailoring power — the real Kuwei is still hidden with the crew. Furious, Van Eck kidnapped Inej and gave Kaz seven days to produce the genuine Kuwei in exchange for her life and the crew's payment.

The book ends with Kaz refusing to hand over Kuwei immediately, choosing instead to protect Inej by other means: he sells his shares in the Crow Club and the Fifth Harbour to raise funds, and turns to Pekka Rollins — the gang leader who caused the death of Kaz's brother Jordie, and whom Kaz had deliberately spared/freed during the Ice Court heist — as part of a new scheme. Going into the next book, open threads include: Inej's captivity under Van Eck, Nina's ongoing jurda parem addiction and withdrawal, the real Kuwei's hidden whereabouts and value as a bargaining chip, Wylan's fractured relationship with his father and his concealed illiteracy, Matthias's vow to Nina and his uncertain standing with the drüskelle after turning on Jarl Brum, and Kaz's brewing plan for revenge and repayment involving Pekka Rollins and Van Eck.