When Caroline Marris joins her sisters, Gracie Gold and Sam Carter for a Nantucket Island getaway, she has no idea how it will change her life. The sisters stumble upon Misty Harbor Inn, the place their late mother loved so much, and Caroline talks her sisters into buying the beautiful but dilapidated inn. But can free-spirited Caroline stay focused enough to make opening the inn a reality? Hand-drawn old postcards draw the sisters into the mystery of Hannah Montague, the young widow of the original owner. Can the sisters uncover the fate of this woman who disappeared in 1880? As Caroline and her sisters work together to make their mom's dream a reality, they bond in ways they never expected.