Kingsbridge sits at the head of an estuary that meets the sea at Salcombe.
Mathilda Rainbird, the elderly, highly intelligent if unusual unmarried daughter of a marine biologist, lives in her odd three storied house in a cove on the South Devon coast. She owns a cottage, also in the cove, which she lets to Isobel Stangate in return for a modest rental and help around the house. Isobel, having left her husband to have a mad fling with a lover only to regret it all almost at once, remains estranged from both her husband and her beloved daughter.
Mathilda, suffering from terminal cancer, decides to take matters into her own hands. She has no close relatives and instructs James Barrington (now working in a Plymouth practice) to make out a new will leaving the cove to three cousins, none of whom knows her nor each other. Satisfied with having made these arrangements she takes out her launch one night . . .
The three beneficiaries are: Tessa Rainbird, an orphan in her early twenties; Will Rainbird, a retired widowed diplomat who has been living in Switzerland; Beatrice Holmes, recently retired school matron. Will and Tessa both fall in love with the cove and wish to keep it. Beatrice is less sure that this is possible. Life is complicated by Tessa becoming engaged to Sebastian, the brother of one of her school friends, and then falling in love with Giles Webster.