At the Parasites Club, the porter reminds resident Charles Luton, Jack Buchanan that his subscription is overdue. Charles dismisses the reminder, asking to be notified later. At the bar, he laments to the barman about feeling overwhelmed by his numerous lady friends. When the barman suggests marriage, Charles scoffs, saying women are difficult to understand. He points to his niece Josephine Luton, Glynis Johns as an example, describing her as overly soft-hearted and always trying to rescue helpless men.
Charles is relieved when Josephine becomes engaged to successful businessman Alan Hartley, Donald Sinden. However, Alan introduces her to his old school friend, David Hewer, Peter Finch, an aspiring playwright living in squalor, unable to finish a play. For Josephine, David becomes her new project. Within weeks, she breaks off her engagement to Alan and announces that she will marry David, although David is unaware of this plan. David and Josephine, whom he calls Jo, marry, and with Jo's care, David begins writing successful plays. They live in a remote country cottage, where Charles comes to stay for a few days.
One night, Alan visits them, seeking refuge. He explains that his business partner has committed fraud, and although Alan claims innocence, his signature appears on incriminating documents. With no way to prove his innocence, Alan plans to flee abroad and asks to stay until his contact calls with arrangements. Jo, now eager to save Alan, tends to him, giving him David's clothes and shaving kit without asking David. She worries about Alan living alone in exile. David, anxious about being implicated and jealous of her revived attention towards Alan, demands that he leave. After a heated argument, David storms off to the pub. Charles follows David.
David rushes home after realising Alan is alone with Jo. Charles follows him back to the cottage. They return to find the house empty. Charles discovers a farewell note from Jo but hides it from David, who assumes she has run off with Alan. Drunk and distraught, David confesses his feelings of being smothered by Jo's care but says he still loves her. Meanwhile, Jo and Alan, escaping in her car, are stopped at a police roadblock. After being taken to the station, they learn that Alan's partner has been found dead, having apparently committed suicide and left a note taking full responsibility for the fraud. Jo realises Alan no longer needs her and decides to return to David. Back at the cottage, Charles encourages Jo to revise her note, saying only that she gave Alan a lift and will return. Jo wakes David, shows him the new note, and they reconcile.
