Clara Hilton Margaret Rutherford is a shrewd, yet kindly old woman who has long been overlooked by the rest of her family. When her cantankerous uncle Simon Hilton, A.E. Matthews, dies, he unexpectedly leaves her the bulk of his estate—his house, six racing greyhounds, a crooked game, a pub, and a brothel—simply because she is the one person who would look after the dependents he cared about and who was the only one still paying attention during his eightieth birthday party. Clara decides to keep Simon's loyal valet Henry Martin Ronald Shiner on to help her run the estate, and she begins to sense how tangled things really are.
At the pub, Cyril and Maggie Mason run the place and try to shield Clara from learning the full truth about their line of work. Yet Clara’s instincts sharpen as she uncovers the darker business behind the doors she’s inherited. She also discovers that Simon’s supposed “natural daughter,” Julie Mason Jill Bennett, who was supposed to receive a small monthly sum for life, has vanished from sight. Determined to find her, Clara asks her solicitor Charles Willis Nigel Stock to track Julie down, only to learn that Willis himself met Julie at the funeral and is dining with her that very evening, a clue that unsettles Clara even more.
Her next lead takes her to the betting world. Fosdick [Eddie Byrne], the man running the crooked Gambler’s Luck wheel of fortune, is already set to perform at Epsom Downs, and Clara goes to confront him. With the police closing in, Fosdick exits in haste, leaving Clara to take charge of the operation. She and Henry are briefly taken into custody, but Charles quickly clears up the confusion and clears her name.
Meanwhile, Alfie Pearce [Reginald Beckwith] and Lily Pearce deceive Clara by pretending the greyhounds they train for her are champions, though the reality is far from it. The tension between Clara and the Masons grows as Charles uncovers that the family has not been paying Julie her monthly allowance. During a private confrontation, Cyril Mason admits their rationale, claiming Julie has no morals; Charles responds with a blow, and later Julie and Charles themselves become a couple.
Clara stages a fundraiser for a children’s holiday fund, but the donations come up short. Henry unexpectedly suggests a new way to boost interest by offering Gambler’s Luck to the patrons, and Clara decides to give the game to Fosdick, stipulating that half the winnings go to her charity. The day of the greyhound races arrives, and Alfie substitutes a different dog for his loser, hoping to rig the result. Clara, however, feeds the chosen dog hot dogs beforehand, causing him to fade and costing Alfie and Henry both money and cups. Clara’s own bet proves victorious because she had wagered on another dog, and afterward she covers the losses owed by the others, setting a tone that she expects fair play from now on.
In the final act, Clara visits Gladys Smith [Fay Compton], the aging brothel-owner, and learns that her own days are numbered. Clara makes clear that she has little time left and that she is the last responsibility Uncle Simon left her. When Clara dies, her will bequeaths the house and funds to support the women who work there, ensuring their welfare, while the pub passes to Henry, securing his future and the family’s legacy in a surprising, if unconventional, ending.