Feyre spends the next day in Adriata feeling increasingly guilty as she walks the city with Tarquin, meets his people, and prepares to betray his trust. She tries to justify the theft by telling herself that Tarquin would not surrender the Book voluntarily and that stopping Hybern matters more than Summer Court goodwill. When Tarquin kindly escorts her home, buys her food, and kisses her cheek good night, Feyre is nearly overwhelmed by shame, but Rhysand silently reminds her to stay focused.

That night, Feyre changes into Illyrian fighting leathers and joins Amren for the theft while Rhysand flies overhead to monitor the guards. At low tide, Feyre and Amren cross the muddy causeway to the submerged temple and search its dark interior without lights. Guided by the Book's unnatural pull, they dig through mud in the center of the chamber until they uncover a lead door, confirming the object has been deliberately sealed and hidden for ages.

To open the first lock, Feyre uses what she learned from entering Tarquin's mind and makes herself into an echo of his identity and power. The door responds to Tarquin's essence and opens onto a spiral staircase leading downward. Feyre and Amren descend into freezing, foul water and follow the Book's power through a hall to a second lead door, which Feyre opens the same way, though the effort leaves her weakened and close to collapse.

Beyond the second door, they find a dry inner chamber protected from the surrounding water by an invisible barrier. In the center stands a pedestal holding a small lead box that contains the Book and bears both Tarquin's seal and the object's own terrible presence. As the tide begins to return, Amren confirms there are no visible wards and tells Feyre she must take the box herself.

Feyre steels herself, again invokes Tarquin's authority, and lifts the lead box from the pedestal. The object immediately rejects her deception: an ancient voice calls Feyre a liar, and the chamber door slams shut. The theft succeeds only for a moment before the hidden sanctuary reacts, leaving Feyre and Amren trapped inside with the Book.