Cassian and Nesta realize Lanthys’s cell is open, and Cassian immediately understands that the Harp must have loosened more than Nesta’s bindings when she used it. Lanthys taunts Cassian, circles them in mist, and begins to sense what Nesta is, while Cassian tries to keep the creature’s attention on himself long enough for Nesta to escape. When Lanthys gets too close to revealing dangerous truths about them, Cassian attacks, orders Nesta to run, and throws her his glowing Siphon so she can find the way out.

Nesta obeys at first, sprinting up the Prison path while Cassian fights behind her and the other trapped monsters begin reacting to the disturbance. As she runs, Nesta connects the Harp’s twenty-six strings to Merrill’s theories about dimensions and realizes the Harp may not only open doors but move someone through space. Before she can escape, Autumn Court soldiers sent by Briallyn appear inside the Prison, proving Briallyn has found her. To save Cassian before the soldiers reach them, Nesta uses the Harp’s first string and transports herself back to him.

Nesta returns to find Cassian badly wounded and unable to kill Lanthys in his shifting mist-form. Lanthys hurls Cassian into the wall, then throws Nesta aside as well, but seeing Cassian injured jolts Nesta out of fear. She rises with Ataraxia, assumes the fighting stance Cassian trained into her, and discovers that the Made blade forces Lanthys into a solid body and terrifies him. While Cassian regains consciousness behind her, Nesta drives Lanthys backward toward his cell and realizes that the supposedly unkillable being fears her sword.

Lanthys questions Nesta’s nature, recognizes that she took power from the Cauldron, and tries to seduce her into joining him as his queen. He offers visions of conquest, restored ancient power, and sexual domination, hoping greed and desire will sway her. Nesta sees through the illusion because Lanthys’s hunger for the Crown reveals that his promised rule would be built on coercion and because she refuses his claim over her body and future. When Lanthys threatens Cassian again, Nesta prepares to kill him.

Cassian uses the opening to throw a dagger into Lanthys’s chest, and Nesta follows with Ataraxia, beheading him. His death terrifies the other prisoners, whose screams echo through the mountain, and the advancing Autumn soldiers hesitate. Knowing Cassian is too injured to flee on foot, Nesta refuses to fight the soldiers, picks up the Harp, and uses three strings to transport them to Feyre’s riverside house in Velaris. Rhysand rushes out as they arrive, and Cassian collapses on the lawn from his injuries.