Elizabeth Sunderland—a forty-three-year-old wife and mother of two teenagers—is the oldest of five children in a blended family that never quite blended. The only thing that has held them together is the iron will of their wealthy parents: Benjamin Sunderland, a venture capitalist, and Kate Bernard, a partner of a hedge fund. Together, Benjamin and Kate create and rule over a Manhattan dynasty of which their children each bear their own unique scars.

Elizabeth has been trying to keep the family together since she was ten years old, hoping to convince everyone they have more in common than just their fortune. This stance will be put to the ultimate test when Kate dies with one final request: that the family travel together to the island of St. John and spread her ashes in the ocean. However, Kate's plan to fix the family will involve more than just a family trip to the sea.

As the hidden secrets and quiet betrayals built up over thirty years begin to ripple and crash like the ocean surrounding the sinking family, Elizabeth not only faces each of her sibling's personal inflection points—moments that could lead to reconciliation or ruin—but she has to face her own demons that have laid dormant. What happens next will shock Elizabeth into recognizing a reality she had no idea existed.