Oro brings Isla to the specter and explains the situation. Isla reluctantly allows the spirit to possess her in exchange for Oro’s promise that he will grant her access to the library on Sun Isle. The specter is attracted to Oro and attempts to seduce him while haunting Isla, but he rejects her. When the ghost leaves Isla, Oro declines to take her to the library immediately. In response, she calls him “a self-centered, heartless wretch” and says that she’s done working with him (462). A few days later, Oro and his friends discuss the possibility that Isla could become their friend and ally, and he resolves to mend their strained partnership.

Oro speaks to Isla, and she agrees to resume their partnership. The next day, a ball is held, and Oro stares at Isla, awed by her beauty. He finally admits to himself that he cares about her. Isla leaves the ballroom and dances with Grim in a separate chamber. The sight of them together devastates Oro.

Suddenly, the island and the palace begin to shake and crumble, and Oro is struck with agonizing pain. Isla urges him not to give up, and he uses his emotions to fuel his magic, a decision that stops the quake but nearly kills him. He initially suspects that Grim caused the disaster, but then realizes that the island is dying along with him.

In an effort to learn about the heart of Lightlark, Isla uses herself as bait to lure out a group of ancient creatures who despise Wildlings. The creatures’ leader, Remlar, says that the heart “blooms only where darkness meets light” (476). In return for this knowledge, he asks that Isla visit him again later.

On their way back to the palace, Oro faints. Isla drags him into a cave so that he won’t be burned by the sun. To pass the time until sundown, she proposes that they ask one another questions. She asks him if it’s possible for true love to exist between rulers. He answers that it isn’t, inwardly worried that she has feelings for Grim. She shares that she feels trapped in a miserable, isolated life, and Oro empathizes. When she refuses to tell him the secret she saw in her tea during his challenge, he offers to let her claim the heart of Lightlark along with the immense power it’s believed to confer on the wielder. However, she declines.

A few days later, Oro and Isla visit Moon Isle, and the oracles tell them that the heart of Lightlark is on that island. Later that night, Isla comes to him in tears and tells him her greatest secret: “I was born powerless” (491). Oro thought that she was using Wildling magic to make him attracted to her, and he realizes that his desire for her is genuine. Oro recognizes that Isla’s inability to access her powers is linked to her immunity from the Wildlings’ curse, which confirms that she doesn’t have to eat hearts or kill anyone she falls in love with.

In a lucid dream, Oro meets Isla on a cliff overlooking his favorite beach and confesses that he both loves her and despises her effect on him. He concludes, “I wish we were not enemies. But we are” (494). When he awakens, he announces Isla’s secret to the other rulers, and Grim vanishes with Isla to protect her. Oro’s declaration increases Cleo’s interest in working with him, and he hopes that she’ll help him find the heart on Moon Isle.

Cleo grants Oro access to a maze on Moon Isle, but the heart isn’t there. Discouraged, he regrets the pain he caused Isla by revealing her secret. Oro discovers that a group of Moonling men have captured Isla and intend to eat her, and he kills all of them before bringing Isla back to the castle. He explains that his apparent betrayal was all part of his plan and that he still intends to let her claim the heart. He also reveals that his flair lets him tell when people are telling the truth, and he insists that he’s never lied to Isla despite the many lies she’s told him. Isla agrees to remain his partner, and Oro is grateful that she “cares about her people more than she hates [him]” (505).

During the Centennial, the rulers hold a public festival called Carmel. Isla becomes intoxicated at the celebration and wanders the palace gardens while singing. Oro takes her back to her room, where they share some tea and fall asleep together.

When Oro awakens later that night, he realizes that he hasn’t made his required appearance at Carmel. In a tone that is “flat and perhaps cruel” (513), he informs Isla that the two of them will search the heart’s two remaining possible locations the next two nights and then conclude their partnership. Oro goes to the festival but keeps to himself, thinking longingly of his mother and brother. Suddenly, Oro hears Isla scream. He rushes to her side and sees that someone has attacked Celeste.

On Moon Isle, Oro and Isla search a sunken castle. He voices his curiosity about her sexual history, but she declines to answer. Isla is attacked by a monster, and Oro uses his magic to heal and warm her. Neither of them find the heart, leaving only one location on Oro’s list.

With only 20 days left in the Centennial, Oro and Isla look for the heart in the final place on his list, which is located in the Vinderland wilderness. When their search proves fruitless, Isla screams and cries in rage. Oro carries her back to the castle, wishing that he could rekindle her hope. Enya encourages Oro by revealing that, according to the oracle, she’ll survive past the Centennial, which suggests that Oro and his realm will too.

With Calder’s help, Oro goes to Vinderland and meets with a local leader in the hopes of learning about the heart. The men that Oro killed for capturing Isla belonged to the leader’s sect, and he demands Isla in exchange for aiding the king’s search. When the man vividly describes how he wants to kill the Wildling, Oro unleashes his fire magic “until every trace of him is gone” (524). Calder cautions Oro that the leader’s death will likely lead to war.

Oro and Isla continue their search for the heart of Lightlark. They discuss their plans for after the curses are broken. He dreams of uniting the realms once more, and he’s saddened to learn that she plans to return to her distant home on the Wildling newland. Suddenly, the island begins to shake again, and Oro is struck with pain. Isla sings to comfort him.

At sunrise, Isla and Oro find the heart of Lightlark, which takes the form of a glowing orb. He hides from the sun in a nearby cave while she goes to retrieve the heart. The Vinderland men return and shoot Isla in the chest with an arrow. Distraught, Oro burns them all to ashes. Grim appears and portals Isla away. Alone in the cave, Oro tries to bargain with a higher power for Isla’s life. He promises that he’ll let her be with Grim if that’s what she wants and resolves not to “scare her with [his] feelings” (535). Oro hurries back to the castle, where he finds that Isla is healed and gives her the heart.

Oro gathers the rulers and asks them to vote for which realm should be sacrificed to break the curses, and the majority nominate Nightshade. Isla is distraught and departs from the castle with Grim, leaving behind the heart of Lightlark and a note for Oro. An explosion of Starling power shakes the palace, and Oro realizes that Celeste is much stronger than should be possible given Starlings’ short lifespans.

Oro finds Isla at the Place of Mirrors, where Celeste incapacitates both him and Grim. The Starling reveals that she is Aurora. Knowing that love allows rulers to access one another’s magic, she schemed for Oro and Grim to fall in love with Isla so that Isla would have access to all of the realms’ powers, which Aurora intends to steal. She also reveals that Grim knew who she was all along. However, he hid this from Isla because Aurora tricked him into believing she would help him.

Isla uses the heart of Lightlark to defeat Aurora and kill her best friend. This fulfills the prophecy because Aurora had killed Violet, meaning that “the original offense [has been] committed again” (543). When the Place of Mirrors falls apart with the force of the curses breaking, Oro saves Isla by using Wildling magic. This prompts him, Isla, and Grim to realize that she loves him. Grim storms away.

Weeks later, Isla emerges from her grief over Celeste. Oro visits her, and she rests her forehead against his. As he reflects on the love they share, he feels that the “world might be worth saving” and that the two of them “could be the ones to save it” (545).