Nova McIntosh has been called many things—a witch. Dangerous. The girl with fire in her hair and salt water in her veins, whose eyes will drag you in and crush your heart like an under tow—and they're all true.

It's said that Loch Moira was once home to a flock of selkies, until its fishermen made a deal with a sea witch to steal their pelts. Unable to transform, the selkies were forced to retain their human forms and wed their captors. But the sea is unforgiving and eternal and demands restitution: the lives of two girls after every storm as penance for the selkies who perished on land, or it will swallow the town whole.

The youngest in a long line of magical women bound to perform these sacrifices, Nova understands the need to be cold and merciless. So, when she finds a boy washed up on the beach after a storm, she doesn't expect to feel anything for him. However, the ocean has never given back anything alive, either, and the closer Nova grows to Arron, the closer she comes to unraveling the mystery behind his survival and discovering the key to ending her town's curse.