When mute assassin Nyx Selvari is captured and forced onto the ship of a brooding, silver-eyed king who looks at her like she is a ghost, she discovers their uneasy alliance hides a devastating secret: he was betrothed to the forgotten princess she used to be, and the dark bargain he struck to save his crumbling kingdom requires him to deliver her to the monster beneath the waves.
As buried memories surface and his heartbeat becomes the only metronome that can teach her trapped power to sing, the line between captor and protector dissolves into a slow, dangerous, consuming fire that neither of them can walk away from.
But the leviathans are dying, the islands are falling, and the force sealed inside her chest will either wake the sleeping gods or destroy the woman he has spent twenty years learning to love.
What happens when the only voice that can save the world belongs to a woman who has never spoken, and the man who needs her most is the one who promised to sacrifice her?