When Sharon Cooper and her daughter, Callie, open a locked trunk in her estranged mother's attic, they find the first in a series of unwanted discoveries. Sharon grew up as an only child – but there are letters from three half-sisters. More secrets reveal theft, blackmail, an affair and murder. Clues are found in a hidden safe, a secret room with reports from a private investigator, a painting from an unknown artist and a personal planner. Despite the awkward circumstances, Sharon connects with her previously-unknown, extended family and she finds the mother figure she always needed in her newly discovered aunt.