In 1959, Hollywood ingenue Mercy Welles seems to have the world at her feet. Far removed from her Nebraska roots, she has crafted herself into a glamorous Oscar-nominated actress engaged to an up-and-coming director...

Until she shockingly vanishes without a trace, just as her career is taking off.

Almost sixty years later, Kit O'Neill, a junior television producer in Manhattan, is packing up her recently deceased grandmother's attic, only to discover a long-lost box of souvenirs that reveal that the grandmother who raised her and her sister Claire was, in fact, the mysterious Mercy Welles.

Putting her investigative skills to use, Kit is determined to solve the riddle of her grandmother's missing life, and the trail eventually leads to Martha's Vineyard.

Mercy retreats to the island nursing a broken heart, only to be drawn to the roguish Ren Sewards, who is not just the simple oysterman he appears to be but a scion of one of the island's wealthy founding families. With her attraction to Ren quickly growing, Mercy soon finds herself entangled in the intrigues of the tightly knit community and the secrets of the Sewards.

Alternating between Mercy and Kit's timelines, including excerpts from letters Mercy wrote the summer she disappeared, The Lost Letters from Martha's Vineyard unfurls into a heart-stopping story of love, betrayal, and even murder.