The Goddess of the Sun once descended from the heavens to grant humans life through fire. Today, she is revered as the protector of knights, ensuring their victory. In the Mormeratta Kingdom, Hildegar Aelius, a mysterious woman blessed with the deity's powers, once led a war that brought the North to its knees. But now, Hildegar bears a cruel curse: when night falls, her body burns in excruciating pain.

Desperate for a remedy and eager for privacy, Hildegar's closest aides seek a healer who can treat her without meeting her. Fate brings them to Erkin, a kind Northern pharmacist whose parents Hildegar killed in the war. His rare knowledge provides temporary relief, leading Hildegar to summon him to her castle to find a permanent cure. Still, Erkin remains unaware that his secretive patient is his parents' ruthless murderer.

After Hildegar spilled rivers of Northerners' blood, her life now rests in the hands of one. Drawn to something familiar in Erkin's gaze, Hildegar approaches him disguised as a handmaiden named "Kaya." But in doing so, she risks realizing the true cost of her actions and the depth of Erkin's inextinguishable desire for revenge.