In 1961 London, a bright 16-year-old schoolgirl named Jenny Mellor is on the exciting path to potentially being accepted at Oxford University. Her studies are closely monitored by her strict father, Jack, while her conservative parents, including her mother Marjorie, aim to support her ambitions. They trust her completely and allow her the freedom to explore her interests, yet they are extremely disapproving of the various boys Jenny brings home, especially when they lack direction in their lives. Jack has a particular disdain for what he refers to as "teddy boys," young men who seem uncertain about their futures.
One rainy evening, after a youth orchestra rehearsal, Jenny finds herself waiting at a bus stop when she meets David Goldman, an older man who stops in his car to express concern for her cello getting wet. As a music lover, he persuades her to let him take the cello in his car while she walks alongside. Once inside his vehicle, they share a delightful conversation about music, and Jenny reveals her aspirations of attending university. David later surprises her with flowers delivered to her home, wishing her luck for her concert. Their budding relationship takes off as Jenny eagerly accepts an invitation to a concert and dinner with David and his friends.
Although her dad is initially skeptical, David's charm wins Jack over, granting Jenny permission to go out. During the concert, she becomes enchanted by David's affluent and sophisticated friends, especially a captivating woman named Helen, who serves as a mentor figure. Jenny is drawn to their glamorous lifestyle and craves to be part of their world. She starts spending more time with them, which unfortunately leads to a decline in her academic performance.
As David's influence grows, he convinces Jenny's parents to allow her to join him on a weekend trip to meet her favorite author, Clive Lewis, supposedly giving her a taste of the cultural life she desires. That night, although David respects her boundaries and does not pressure her sexually, they share intimate moments. Later, Jenny presents her parents with a signed copy of The Lion, the Witch and the Wardrobe, believing it came from a meeting with Lewis, when in reality, it was a trick by David.
As time passes, Jenny discovers the alarming truth about David—he is a con man involved in dubious activities. Despite her initial shock, she suppresses her doubts, continually enchanted by David’s charisma. For her 17th birthday, he takes her to Paris, a lavish getaway filled with sightseeing and dancing, resulting in them losing their virginity to each other. After fulfilling her romantic fantasies, she tries to share her happiness with her favorite teacher, Miss Stubbs, who expresses concern over Jenny’s relationship with David, leading to a painful confrontation between them.
When David proposes marriage, Jenny—having been swept up in the romance—accepts, deciding to drop out of school, much to the dismay of her teachers. Although her parents seem unperturbed, believing that David will provide for her, she remains blind to the precariousness of her situation.
The truth strikes hard when Jenny discovers that David is already married. Devastated, she confronts him, feeling betrayed for giving up her education and future for him. After an emotional confrontation, David promises to make things right but disappears, leaving Jenny lost and hurt. She channels her anger towards Danny and Helen, blaming them for not revealing David’s true nature, alongside her parents whom she believes enabled her poor choices.
Desperate for answers, Jenny visits David's wife, who reveals the extent of David’s deceit and infidelity, shattering Jenny's illusions. It's a harsh awakening, but through the realization of her mistakes with David, she gains a stronger perspective on her own choices. Her father, Jack, apologizes for his misguided trust in David, elucidating how illusions can distort reality.
Determined to reclaim her future, Jenny seeks out Miss Stubbs to repair their fractured relationship and earn back her place in school. With unwavering support, she resumes her studies and is ultimately accepted into Oxford. In a reflective closing voiceover, Jenny expresses her newfound understanding of relationships, eager to start fresh while drawing wisdom from her past experiences.
