The next day, Isla and Grim enter the Caves of Irida and see that a dragon is guarding Cronan’s sword. As they approach the blade, arrows fire at them. Grim shields Isla with his body and is shot 12 times. He portals them to his room, where she tends to his injuries and makes him laugh. He tries to convince her of the truth of his father’s maxim that “[p]ain makes you powerful” (149). She argues that he can’t be as monstrous as his reputation claims since he risked his life to save hers.

Grim and Isla make several more attempts to claim the sword. The more time he spends with her, the stronger his feelings for her become, but he resists his desire to tell her how he feels.

Grim hosts a ball at his palace to boost his realm’s morale. He orders Isla not to come, but she attends anyway. Grim is filled with envy as he watches a man dance with her, and his jealousy turns to rage when he realizes the man drugged her drink. Grim kills the man and gives Isla an antidote that restores her presence of mind. When Grim admits to having sexual fantasies about her, Isla says, “I would rather die than have you touch me, demon” (161). However, he doesn’t sense any hatred from her.

Grim doesn’t want Isla to die, so he attempts to defeat the dreks without Cronan’s sword. He envisions marrying Isla and having a child with her, and his powerful emotions destroy hordes of monsters. However, his feelings distract him, and one of the dreks poisons him. Grim portals himself to Isla’s room and asks her to heal him with a Wildling flower. As he loses consciousness, he muses that he can die happily now because she would be the last person he sees. He dreams of sharing a life with Isla and feels “thoroughly, infinitely, and wholly happy” (166).

When he awakens, Isla demands to know how he was injured. Even though it’s considered treasonous to reveal Nightshade’s vulnerabilities, he explains that dreks began pouring through a rift called the scar centuries ago. He adds that his father wanted Cronan’s sword so that he could use the dreks to attack Lightlark, but Grim only wants to banish the monsters. Isla asks Grim about his mother, and he says that he never knew her. Isla says that the tradition that forbids Nightshade’s rulers from falling in love must make him lonely. He lies to her, claiming he isn’t lonely and has no interest in love.

The narrative moves a few weeks forward. Grim and Isla repeatedly try to sneak past the dragon and booby traps that guard Cronan’s sword without success. Their progress is hampered by the curse on the weapon, which prevents Grim from using his powers near it.

After another failed attempt, Grim and Isla tend to their wounds and discuss his ability to sense other people’s emotions. He longs for Isla to reciprocate his feelings for her. However, he doesn’t think he has a right to ask this of her because he’s shown her only “harsh words and repulsive actions” (177). Their conversation turns to their kiss, and they both reveal that it was their first kiss. Tension builds between them, but he leaves because she doesn’t say that she wants him to kiss her again. That night, Grim returns to Isla, watches her sleep, and says that he would choose her if he had “any right to happiness at all” (177).

Grim realizes that nightbane, a plant that the people of Nightshade turn into a highly addictive drug, is the same plant that Wildlings use to make medicine. He brings Isla to a field of nightbane flowers and explains that they’re “a bridge between [their] two realms” (180). She proposes a deal in which the Wildlings would give the people of Nightshade healing elixirs in exchange for nightbane plants, and he accepts.

Sensing a shift between them, Grim asks Isla if he can kiss her, and she nods. As he leans in, he senses another drek attack and portals away. Grim is distracted by thoughts of Isla during the ensuing battle with the monsters, but he returns to his room uninjured. Isla is waiting for him on his bed, and she asks him to touch her. They share a passionate kiss and then have sex.

Grim and Isla practice navigating the caves’ booby traps until they’re certain they’ll succeed. To celebrate, Isla proposes that they attend a hot air balloon festival in the Skyling realm. Grim has no interest in the celebration, which seems “too crowded. Too loud. Too joyous” to him (197). However, he enjoys seeing how happy it makes her. During a hot air balloon ride, Grim overcomes his fear of heights when Isla becomes nervous and turns to him for comfort. At her request, he portals her back to her room. She wants to have sex, but he insists that they sleep side by side platonically because she’s been drinking.

The next day, Isla and Grim search a Starling marketplace for something they can use to distract the dragon. They kiss in an alley. Isla wants to have sex there, but Grim stops them from going further because of his guilt over the secrets he’s keeping from her.

Over the next few days, Grim tries to find a way that he can claim the sword without Isla dying. He realizes that a “love bond” could save her and allow him to protect his realm, but he doesn’t believe he’s capable of love. Refusing to let Laila’s death and everything else he’s endured be in vain, he sticks to the plan to claim Cronan’s sword.

On the day that Grim and Isla return to the cave, he feels emotionally numb and distant. However, he abandons the plan and races back into the cave when he realizes that the dragon isn’t following him. He unleashes his powers to protect Isla from the dragon’s flames even though doing so makes the sword vanish. Grim portals Isla to her room. Although he’s filled with fear for his realm, he doesn’t regret his actions because he believes “the world will be better” if Isla lives and he perishes (212).

Isla is shocked and furious that Grim abandoned their plan. She asks if he’ll still honor their agreement and help her at the Centennial, which is about six months away. Although he secretly never intended to go to the Centennial and isn’t certain that he will live long enough to attend, he resolves to defend her as long as he can.

Grim almost tells her that his plan to claim Cronan’s sword would have killed her, but he hesitates. She admits that she doesn’t have access to her magical powers, and he assures her that he already knew this: “Nothing, absolutely nothing, is wrong with you, heart” (219). They have sex and fall asleep together. When Isla awakens, she fears that Grim will leave her because Nightshade’s rulers aren’t supposed to sleep with the same person more than once. He laughs and assures her that he isn’t going anywhere.

Isla begins spending her nights at Grim’s palace, and Grim uses illusion magic to conceal her absence from her guardians. Much to his chagrin, she gives him a baby dragon, and he’s forced to share her attention with his new pet.

One day, Isla brings Cronan’s sword to Grim and demands to know the full truth of his plan. He explains that her father was from Nightshade and that breaking the curse on the sword would kill her. Through tears, she tells him that she never wants to see him again.

Without Isla, Grim’s existence feels like “pure and utter torture” (234). Weeks after the last time they spoke, he senses a large drek incursion and is certain that he will perish fighting the monsters. Before he heads to battle, he brings the baby dragon to Isla and tells her that she means everything to him: “What I feel for you can never be extinguished [….] You and me…we’re infinite” (235). Isla cries and insists that she can help him, but he takes her starstick so she can’t follow him into danger.

As Grim fights the dreks, Isla portals onto the battlefield. In this world, love allows people to share their magic with one another, and Grim realizes that he must love Isla. When Grim is gravely wounded by a monster, Isla unleashes all of her dormant powers. Although she succeeds in destroying the dreks, expending all of her power is lethal. With her dying words, she tells Grim, “Pain is not the strongest” (240). Grim revives Isla by binding his soul to hers.

Days later, Grim brings Isla back to the field of nightbane flowers. She tells him that she loves him, which is the first time anyone’s ever spoken those words to him. He replies that the word “love” doesn’t adequately convey his feelings for her: “I live for you. I destroy for you. I die for you” (244). He kneels before her and asks her to marry him, and she joyfully accepts.

The narrative moves ahead to Grim and Isla’s wedding date, which is the first time that a Nightshade ruler has ever married. Her dress is stitched with “curls of shadows, meeting colorful flowers” to represent both their realms (246). In their vows, they pledge to share “a union of minds and souls, for the rest of time” (248). Grim inwardly resolves to retrieve the Infinite diamond for Isla. As they kiss, he realizes that he and Isla are both shedding joyful tears.