On the morning of her 40th birthday, Alison Penny believes that from now on her life should be nothing but serene and pleasant. That was before Miss Penny met Miss Plum. Victoria Plum was weeping on a park bench and obviously bent on drowning herself in the duck pond...

"I do not anticipate for one moment that Miss Plum has been murdered, though I should have some slight sympathy with her assassin if she had."

Miss Penny is a middle-aged spinster living a cheerful, contented life, complete with perfect housekeeper, in an idyllic English village. Her romantic life consists of an annual Christmas card from her old flame George, and her social swirl involves Stanley, a prissy neighbour who keeps her in mind for a future wife, and Hubert, a neurotic widowed priest with an alienated son.

Into this stable life comes Miss Plum, whom Miss Penny saves from drowning herself in a duck pond and takes into her quiet, orderly home. The villagers embrace the perpetually weepy, forlorn young woman-at first. But soon her welcome wears thin.