Forty-year-old Nora Cunningham has it all: a handsome husband, Malcolm --- the youngest attorney general in Massachusetts state history --- and two healthy, lively daughters, Annie, 7, and Ella, 11. That is, until she and the rest of the world learn of Malcolm’s affair, and his refusal to give up his lover turns their lives upside down.

At the height of the scandal, Nora receives an invitation to visit her maternal aunt on Burke’s Island, off the coast of Maine. To escape the growing political storm and gain perspective on her marriage, Nora packs up her daughters and heads to the remote community, originally settled by Irish immigrants. Nora hasn’t been there since she was three, the summer her mother disappeared and she and her father moved to Boston, never to speak of those months again.

One night, while sitting alone on Glass Beach, below the cottage where she spent her childhood, Nora breaks down at last. Her tears flow into the sea, where, according to local legend, they might invoke a selkie --- a mythic creature --- to console her. Not long afterward, Owen Kavanagh, a fisherman with a mysterious past, is shipwrecked on the rocks.

As the weeks pass, Nora uncovers more questions about her relationships, her mother’s fate, and her own identity. Then Ella undertakes a reckless journey, heading to Boston in a boat that once belonged to her grandmother, her younger sister in tow. Nearly drowning in a storm, the two girls wash up on Little Burke’s, an islet across the channel that plays a recurring role in Nora’s fragmented memories. As she frantically searches for her daughters, Nora finds the courage to chart her own course --- and the secrets surrounding that long ago summer --- finally come to light.