In the winter of 1896, Neema, 16, works as a seamstress. She is a halfling. Her mother was a selkie. Her sister Lila fell in love with a human but was jilted on her wedding day. When Lila is found dead in the rocks of the town's jetty, officials assume her death to be a suicide. Lila is buried outside the town limits since suicides are not allowed in the hallowed ground of the cemetery. The would-be groom is missing.

Neema does not believe her sister would commit suicide. She crawls on the rock jetty searching for clues to prove someone harmed her sister. There she meets Emmett, 17, a new surfman in the lifesaving service. He is drawn to Neema, but she's odd. Yet, when they kiss, their feelings for each other intensify.

The lifesaving dog finds a sealskin along the edge of the shore and fights with a seal for the skin. Emmett kills the seal.

Neema learns of selkies seeking revenge upon Emmett. How can she warn him of the danger?

Neema discovers a hidden room in the cottage of her employers. Are they harboring a criminal unknowingly?

When a nor'easter hits, Neema knows it presents an opportunity for the selkies to enact their retribution against Emmett. As a ship founders offshore, Emmett must go out with the other surfmen to save those on board the ship. Neema shifts into a seal and saves him, but can she save herself from the selkies' revenge?