1951. Esther Durrant, a young mother, is committed to an isolated mental asylum by her husband. Run by a pioneering psychiatrist, the hospital is at first Esther's prison but soon surprisingly becomes her refuge. 2018. Free-spirited marine scientist Rachel Parker embarks on a research posting in the Isles of Scilly, off the Cornish coast. When a violent storm forces her to take shelter on a far-flung island, she discovers a collection of hidden love letters. Captivated by their passion and tenderness, Rachel determines to track down the intended recipient. But she has no idea of the far-reaching consequences her decision will bring. Meanwhile, in London, Eve is helping her grandmother, a renowned mountaineer, write her memoirs. When she is contacted by Rachel, it sets in motion a chain of events that threatens to reveal secrets kept buried for more than sixty years.