Arriving at the honeysuckle-covered beach house inherited from her beloved grandmother, recently heartbroken Jill hopes to convince her two feuding sisters not to sell a place so full of happy childhood memories. But the envelope waiting on the driftwood table changes everything. In her elegant handwriting, Nana Rose promises a new letter will arrive each day of the summer revealing a family secret she took to her grave.

Shaken, Jill anxiously awaits each letter filled with Nana's bittersweet memories of her own sister who she loved more than anyone--and lost far too young. But why did Nana never speak of this tragic loss to her grandchildren?

Watching the sunset each night and wondering how well they really knew Nana Rose, Jill feels her family is closer than they've been in years. And after a chance encounter with blue-eyed tree surgeon Alex, she wonders if Nana believed being back on Dune Island would help Jill find love, too?

But when Nana's final letter arrives, the revelation about how her sister died is more shocking than Jill ever imagined. Suddenly, despite the chance of happiness with Alex, selling the house seems the only way forward. Will Jill find a way to forge new bonds of sisterhood and save their inheritance, or will Nana Rose's secret tear them all apart?