It's 1961 and Jenny (CAREY MULLIGAN) is a 16-year-old who lives at her Twickenham, England home with her parents, Jack (ALFRED MOLINA) and Marjorie (CARA SEYMOUR), attends a private all-girls school run by the Headmistress (EMMA THOMPSON), and who would seem to have everything going for her.
Bright, cultured beyond her years, pretty, and the best student in her English class taught by Miss Stubbs (OLIVIA WILLIAMS), Jenny is working hard to get into Oxford, all while enjoying the attention paid to her by fellow musician Graham (MATTHEW BEARD).
But that teen isn't the only one drawn by her interest in fine music, as thirty-something David (PETER SARSGAARD) offers to give her a ride home in the rain one day, supposedly only in the interest of protecting her cello from the elements.
He also seems to have it all -- a rare sports car, fun friends in Danny (DOMINIC COOPER) and Helen (ROSAMUND PIKE), boyish good looks and a disarmingly charming demeanor -- and his access to the finer things in life lures both Jenny and then her parents into thinking he might be the best thing ever to come along for her.
It's not long before David and his friends are whisking Jenny away to Oxford and then Paris for her 17th birthday, and she loves every minute of her new life. All of which makes her question why she should continue pursuing academics when any achievements in that won't provide her with the same level of satisfaction she's currently experiencing.
As the headmistress and Miss Stubbs try to warn her about continuing this new lifestyle and mindset, and after discovering that everything isn't as perfect as she originally thought, Jenny must decide what to do about her future.