Princess Estyn was born on the wrong day.

While her solstice-born brothers use their magic to command flora and fauna, Estyn can barely control her own life. She dreams of running away, but her plans to escape during the royal ball are dashed when the warring kingdom attacks-and kidnaps her little brother.

Estyn knows little of the outside world, but she can't just leave her brother's fate to politics. So with limited time and an ocean to cross, Estyn must evade capture by her father's soldiers, form tenuous alliances-including one with a charismatic rebel leader-and break into a heavily fortified castle using little more than quick wit and wild shadows or risk losing her brother forever.