The prologue begins with Fehla, the Queen of Caerlon, on the night she gives birth to two children, a boy and a girl. Knowing her husband, King Casréyan, is a paranoid and power-hungry man, Fehla conceals the twin birth from him. Casréyan is desperate to achieve immortality so he can rule forever, and he has never wanted an heir. However, in order to secure the royal line until the moment he achieves immortality, his advisors convinced him to sire one heir. Only one. Fearing for both children, Fehla sends her daughter away before the king can learn the truth.
Over twenty years later, the story opens on a beach outside the village of Faltir, on the north-east edge of Caerlon. Catanya is sitting alone on the beach, sorting through her old sketches and paintings, contemplating her future, when her best friend Diyah arrives to sit with her. Catanya and Diyah grew up together at an orphanage, where they formed a bond like sisters. Diyah—now the last of the ancient race of healers known as the Heiltúir—lost her parents when she was young. But Catanya’s only hint of her parentage is an unusual necklace, bearing an iridescent and multi-coloured gemstone that once belonged to her mother.
Prince Cadyan has grown up, abused and brutalized by a sadistic father, which has warped him into something twisted and dangerous. Now that his father is dead and allegedly poisoned by Cadyan, it is the son’s turn to claim the throne and all the magic of Resonance that has been bound to the kingdom for centuries. However, as Cadyan drinks the elixir of Caerlon to receive his sacred power, something goes wrong. Far away, Catanya also feels its effects, and the force of the magical transference shatters her mother’s necklace. Cadyan and Catanya finally learn the truth about each other.
Enraged by this threat to his power, Cadyan sends his elite soldiers, the fírkon, to hunt down his sister. The soldiers kill everyone at the orphanage, taking Diyah and three of the younger girls prisoner. As Catanya escapes into the forest, she discovers her ability to wield the terrifying magic that, until now, only the King of Caerlon has been able to control.
Diyah is taken to Caerlon City, where she comes face-to-face with the newly crowned King Cadyan. Diyah remembers meeting him as a boy, 10 years before, during his tour of the kingdom. The young prince had been terrorizing and attempting to hurt her when an unknown older boy had intervened, declaring that “a truly powerful man doesn’t find strength by making others feel weak.” Now, meeting Cadyan again as an adult, Diyah realizes he doesn’t recognize her. She also remarks that his naturally black hair has transformed into an otherworldly mixture of colours, silver and opaque with hints of rose, turquoise, and violet. He commands his soldiers to escort her to the dungeons for interrogation.
Stumbling through the woods, Catanya meets Jémys, a kind and handsome villager with a strong moral code and sense of responsibility. Together they encounter a gang of outlaws who attempt to rob them. In the ensuing fight, Catanya harnesses magic again, using it to fend off an attack, incapacitating the outlaws. The leader of the outlaws, the provocative and cunning Drayk, seems to be the only one who recognizes the magic. Catanya and Jémys leave him tied to a tree, but Drayk gleefully vows that he will find them again.
In Caerlon City, Diyah is being tortured for information about Catanya. She refuses to divulge anything, even when the slimy Maífírkon, Slaedir, becomes increasingly vicious and perverse. A second soldier, an emotionless and shrewd fírkon named Julyán, suggests torturing the young girls to force her to talk. He also recognizes the sign of the Heiltúir on her satchel and informs the king that she could be a useful asset.
Eager to preserve his power and defeat his sister, Cadyan continues his family’s centuries-long search for the fabled Relics of Illayan, three ancient artifacts purported to wield rare magical gifts. The artifacts were created in the time before the Quiescence Wars, before Caerlon’s great founder, Maílater Caer eradicated the widespread practice of Resonance in Mórceá. When at last Cadyan finds one of the artifacts—a ring with the power of compulsion—he finally has proof that the relics exist. He commands his fírkon to redouble their search, desperate to find the last two relics, especially the legendary crown of immortality, so he can defeat his sister and rule forever.
Jémys takes Catanya to his home in the farm village of Finnua, where she meets his aunt Nelle and a precocious young boy, Olly, who idolizes Jémys. Catanya struggles to resist the charm of life in Finnua. Jémys buys Catanya a sketchbook and set of pencils, encouraging her to resume drawing. Catanya uses the art as an outlet for her grief, drawing pictures of everyone she has lost, even drawing images of Cadyan, as she’s seen him in her dreams.
Meanwhile, wasting away in the dungeons of Caerlon City, Diyah receives a surprise visit from Queen Fehla. The queen visits several times, bringing bandages and food, assuring Diyah that she wants to help. She never wanted any of this to happen, and she hates the man her son has become. King Cadyan and Julyán arrive to punish them all, but Diyah bargains for the release of the three girls in exchange for her services as court physician.
After several weeks in Finnua together, Catanya and Jémys fall deeply in love. Catanya learns of nearby raids and, fearing the threat of the fírkon, decides she needs to leave to protect everyone. But Jémys stops her, and they make love in the meadow on the edge of the forest. They awake to find the village in flames. The fírkon decimate the village, killing everyone, including Nelle and Olly. Catanya unleashes her fury for the first time, using her magic to fight the fírkon. Catanya and Jémys escape, but Jémys is heartbroken and furious at her for hiding the truth. Catanya notices her black hair is now lightly streaked with iridescent silvery strands.
Thrust into a life of fear and deceit, Diyah must work for the king she despises under the watchful eye of his dutiful soldier, Julyán. Diyah continues to befriend Fehla while she strives to understand Julyán and unravel the lies and secrets swarming the court of Caerlon. In her new role, she meets Lord Zadílar, the Lord Steward of the city of Sidina. Lord Zadílar uses his irreverent, insincere charm to catch Diyah off guard, but he seems to know more than he’s letting on about her and her ancestry. He warns her that the Heiltúir code of ethics will not protect her anymore, and she must be calculating and vigilant if she wants to survive. He vows to offer her his help, but is interrupted before he can elaborate.
Back in the forest, Jémys and Catanya are struggling to put distance between themselves and the carnage at Finnua, when Drayk and his gang of outlaws descend upon them, capturing them. Drayk seems to enjoy keeping them captive, and he taunts Catanya about her identity and her powers. Eager to see more magic, he tortures Jémys to elicit Catanya’s emotions, forcing her to use her powers. When the other outlaws realize who Catanya is, and that King Cadyan is offering a hefty reward for her capture, they decide to revolt against their leader. Drayk protects Catanya from the other outlaws and he, Jémys, and Catanya escape together. Now the three uncomfortable allies head for Drayk’s cottage by the sea. Tensions come to a head when Jémys declares he doesn’t trust either of them and storms off, seemingly abandoning them.
Cadyan descends upon the cottage with his soldiers. The ensuing battle results in the first confrontation between brother and sister. He tries to use his ring on Catanya, compelling her to return to Caerlon with him and join his family, where they could combine their powers and become unstoppable. Catanya’s love for Diyah, the only family she’s ever known, helps her overcome the ring’s compulsion. A blast of magic explodes between them and she manages to knock Cadyan unconscious. Catanya and Drayk escape by boat into the Kingdom of Awnell, unaware that Jémys—who had returned for Catanya—has been captured by the fírkon.