Wisteria, a count's daughter, quietly loves Bright, a duke's son and her childhood friend who cannot use magic and has been carrying out forbidden research in secret. She is crushed when he admits he loves her younger sister, Rosalie. When Rosalie is chosen to become guardian of the Predawn Realm, a post from which no one returns, Bright asks Wisteria to go in her place, since she is gifted with magic and can withstand the miasma threatening the mortal world. Heartbroken, she enters the realm carrying the sacred sword Sartis. More than twenty years later, a stranger who looks like Bright arrives, demanding the sword and challenging her. The result is a fantasy drama with action, built around love and sacrifice.