The narrative moves five years forward. As the Gauntlet approaches, the 12-year-old Grim uses his flair to explore various locations in Nightshade at night, including a licorice store. One night, Laila promises to give him a quick death, hugs him, and cries. He reassures his sister that she’ll be a good leader. After the siblings’ conversation, Grim wants to see as much of the world as possible, so he teleports to Lightlark and admires its natural beauty even though setting foot on the other island is considered treason in Nightshade.

The next morning, Grim’s father murders all of his children except for Grim and Laila because he’s discovered that Grim can teleport, which is the same flair that Nightshade’s founder, Cronan, possessed. The ruler demands that Laila and Grim fight to the death. Grim chooses not to defend himself when she tries to kill him, but his shadow magic manifests and destroys her. The Nightshade ruler tells his distraught son that pain is empowering. One of Grim’s guardians carries the numb boy to the kitchen and makes him a cup of hot chocolate. He resolves to put aside his emotions and become his fight on his father’s behalf so that his siblings’ deaths will have meaning.

The narrative moves 20 years forward. Grim’s father has been waging war against Lightlark for five years, and Grim, who is now 32, has gained a reputation as a monster because he’s killed thousands of soldiers in battle. At night, Grim’s father attacks the Sunling castle and kills the king and queen of Lightlark. The Sunling rulers’ younger son, Oro, is filled with “pure rage and agony” as he battles Grim (36).

When Oro claims that Grim can’t understand the grief of “seeing the person you love most die in front of you” (36), Grim’s numbness shatters, and his grief over Laila overpowers him. He hastily portals back to Nightshade. Grim’s father reveals that his health is deteriorating because he tried to claim the Infinite diamond and was cursed by the stone. Because Nightshade lacks the military power to win the war by force, Grim’s father surrenders, hands over his son as a prisoner of war, and orders him to find a way to claim Lightlark from within.

Months into Grim’s captivity on Lightlark, he and Oro survive an adventure together that transforms their hatred into friendship. Over the next two decades, Grim learns to manage his grief and enjoys his new peaceful existence. He occasionally has brief trysts during his time on Lightlark. One of his lovers asks him for a flower from Nightshade, and he uses his flair to retrieve it for her. The woman uses the flower to cast a deadly curse that affects each of the six peoples that make up the world of Lightlark in a different way. Oro assumes that Grim knowingly helped the woman cast the curses, and their friendship is broken. Grim portals back to Nightshade, where his dying father gives him the throne and informs him of a prophecy that claims Grim will seize the Infinite diamond and conquer the world. His last words to his son are a reminder that “[l]ove kills kingdoms” (241).

The narrative moves 499 years forward. Within the world of Lightlark, the lives of each realm’s citizens are tied to their respective leaders. Nightshade’s population dwindles due to the curse that was cast centuries earlier and to attacks from winged monsters called dreks. Grim’s council urges him to have an heir so that the realm won’t perish if he dies. A group of women willing to bear Grim’s child assemble, and he chooses Isla because she’s “the most beautiful woman [he has] ever seen” (51). They share a passionate kiss in his room, and then she stabs his chest with a dagger and flees. He decides to keep the scar as a reminder of the danger of succumbing to desire.

Grim discovers that Isla is the Wildling ruler and that she used a device called a starstick to reach his kingdom. He created the starstick by imbuing it with his portaling flair and gave it to his general 25 years earlier. Determined to reclaim the powerful object and then kill Isla, he spends several nights spying on her but finds no trace of the starstick.

Grim tricks Isla into revealing the starstick’s location to him. She cries as she clings to the object, and her fear and loneliness remind him of how his portaling offered him a taste of freedom when he was a child. Against his better judgment, he decides to let her keep the starstick.

Grim deduces that Isla is the daughter of his previous general, whom he believed dead, and the previous Wildling ruler. Because of the curse on Wild Isle, Wildling women use magic to seduce men and then consume their hearts. Grim suspects that Isla has cast an enchantment of this nature on him, but an augur who uses blood to divine information about individuals and their fates reveals that she didn’t curse him. Grim resolves to stay far away from Isla.

During a battle against the dreks, Grim draws upon his loneliness and grief to make his magic more powerful even though doing so is highly dangerous. He recalls how Isla’s father helped him fight the dreks decades earlier. Grim sent the general on a quest to find Cronan’s sword, an artifact with the power to control the monsters. When the general never returned, he assumed that he’d died. As Grim thinks about how Isla wouldn’t exist if the general hadn’t abandoned his duty to Nightshade, he feels “a mix of happiness and fury” (75).

As the weeks pass, Grim ignores his council’s urging that he choose a consort and produce an heir. One day, Isla uses the starstick to portal into his chambers. She offers him a vial of healing potion for the scar on his chest, but he rejects it. Isla challenges him to a duel, saying that if she wins, they’ll no longer be enemies and they can “begin anew at the Centennial” (80), a gathering of Lightlarks’ rulers that takes place every 100 years and seeks to break the curses on the realms. Grim admires her combat skills as they engage in a swordfight that feels “more like a dance, like a conversation” (83). When he wins, he orders her to stay away from Nightshade. However, he continues to visit her on Wild Isle, using his magic to make himself invisible.

As the dreks’ attacks become increasingly frequent, Grim resolves to find Cronan’s sword. He believes that Isla can help him locate the weapon. Unbeknownst to her, she has magical powers. He suspects that this suppressed power would be enough to break the curse on the sword and allow him to wield it, but this would likely kill her. When Isla portals to Nightshade, Grim has her imprisoned in his dungeons and demands that she help him find the sword in exchange for her freedom. She accepts, not realizing that she “just sealed her fate” (93).

To test whether Isla will be able to help him in his quest for Cronan’s sword, Grim arranges for a blacksmith to chase Isla through a forest. She defeats her pursuer by stabbing him in the eye but twists her ankle. She feels betrayed that Grim ordered the blacksmith to attack her. He’s surprised that she trusts in him because he considers himself “the most dangerous thing she’ll ever face” (95).

Grim makes himself invisible and spies on Isla as her guardians berate her for endangering her realm with her risky behavior. He’s surprised at the protective anger he feels. After Isla cries herself to sleep on her bedroom floor, he carefully tucks her into bed and asks the slumbering woman, “Do you have any idea how many ways you’re killing me?” (98).

The narrative moves forward about two weeks. Isla’s ankle has healed, and she and Grim resume their search for Cronan’s sword. He feels “a flicker of regret” when he considers the fact that she will likely die when they find the weapon (104). One day, an injured Isla portals herself to Grim’s room. He helps her tend to her wounds and then makes her hot chocolate. To distract her from her pain, he gives into his “urge for her to know [him]” and tells her about the brutal training he endured as a child (110).

Grim follows Isla back to Wild Isle and keeps watch over her that night. She explains that she didn’t come to his palace to attack him the day they first met. She accidentally portaled there with her starstick, and a member of Grim’s staff mistook her for a consort. Although Isla claims to hate him, Grim can sense that their attraction is mutual. The next day, Grim teaches Isla how to improve her control over the starstick as well as her swordplay.

Grim and Isla receive a tip that someone who knows the location of Cronan’s sword will attend a celebration at Creetan’s Crag. The event is a masquerade, and Grim is filled with “tender, possessive” feelings when he sees Isla’s dress for the occasion. Grim knows that Isla is unable to access her magical powers, but she refuses to admit this. When he challenges her to use her Wildling magic to seduce a thief who knows where the sword is, she secures the thief’s attention with a dance. After she acquires the information they need, she teases Grim by claiming that she used her Wildling powers on him: “Did I make you fall hopelessly in love with me?” (133). He retorts that he wants to ruin her, not cherish her. They share a passionate embrace before he suddenly portals her back to her room. Grim plunges himself into an icy pool in Nightshade and resolves to resist his feelings for Isla for the sake of his duty.