Miss Jane Marple is asked to help Gwenda, a wealthy young woman who has bought a house on the English coast, only to experience disturbing visions. Thanks to Miss Marple's investigations, Gwenda discovers that, instead of spending all her life in the New Zealand city of Christchurch, she had lived in the house as a child. The visions are actually flashes of memory - and she realizes she witnessed the murder of a beautiful woman named "Helen".