It is the early 1960's, and Jenny (Carey Mulligan
) is a bright young schoolgirl quickly approaching her 17th birthday. Jenny's parents have sacrificed much so that her schooling can get her into Oxford, with her doing everything from learning Latin to playing the Cello.
One day, having been caught in the rain, a much older man named David (Peter Sarsgaard
) helps Jenny get home. Jenny is rather impressed by David's taste in music, as well as his maroon-colored Bristol, a very rare car.
David soon after leaves a bouquet of flowers on Jenny's family's doorstep, and when she sees him in town (with a couple of her classmates in tow), she thanks him for the kind gesture. David then mentions how he would like to invite her to a concert Friday evening. Jenny is unsure if she can get permission, but when David shows up and charms both her Mother and Father, she finds herself spending an exciting evening listening to a concerto, and having a late supper at a supper club.
David then comes calling again, offering to take Jenny on an outing with his friends, Danny (Dominic Cooper) and Helen (Rosamund Pike). They partake some time at an art auction, before going to Danny's place, which is a lavish and luxurious residence. After this, Jenny watches as David moves some West Indians into an apartment house (much to the disdain of a couple neighbors).
David soon after invites Jenny to accompany him and some friends to an outing in Oxford. To get Jenny's parents to consent, David lies about having studied there, and knowing famed author C.S. Lewis, who he claims lives there, and whom Jenny (playing along with his 'game') pretends to want to meet.
David, Jenny, Danny and Helen head off, and while away their first day at a pub, with David forging C.S. Lewis' signature on a copy of "The Lion, The Witch, and the Wardrobe" to pull off the prank.
Later that even, being in the same room as David, Jenny confesses to him that she is still a virgin, and wishes to stay so until she is 17. David tells her he has no problems with this.
The next day, the party stops at a small house, where after a short time, David and Danny emerge from the house with a framed map, and demand the girls return to the car. After they take off and return to London, Jenny stalks off, feeling that David and his friends are a bunch of thieves.
David confesses that they do steal some items for sale, and admits to why he was helping the group of West Indians the other day. This practice, called "blockbusting," involves moving West Indians families into areas where elderly women don't wish to live by them. Wanting to vacate (fearing a possible overflow of 'others'), the old women tend to sell their flats for a cheap price. Jenny then forgives David, and continues on with their relationship.
Soon after, Jenny tells her school friends how David is planning to take her to Paris for her 17th birthday (a place she's wanted to visit for some time). Her friends eagerly give her a wishlist of gifts to bring back for them, but word quickly spreads through the school. Soon, Jenny's teacher Miss Stubbs (Olivia Williams) and the Headmistress (Emma Thompson) have heard, and caution Jenny about what she is doing. However, Jenny still intends to go.
On the day of her 17th birthday, David stops off to deliver a number of gifts to Jenny, and to ask her parents if she can go with him to Paris. Jenny's parents are against this, but David soon manages to charm them into letting her go.
In Paris, the two enjoy a romantic time, before Jenny final 'gives' herself to David.
Upon returning, Jenny attempts to give Miss Stubbs a package of "Chanel No. 5" as a bribe to help her pass over some of her current papers and scores...many of which have suffered from Jenny's lack of attention. Miss Stubbs refuses the bribe, and attempts to talk sense into Jenny again, but Jenny just feels that her teacher is grooming her for a boring and unexciting life, unlike what she is currently experiencing with David and his friends.
A few nights later, David, Jenny, and their friends attend a dog race, at which time, in the parking lot, David proposes for Jenny to marry him. Jenny does not answer right away, and discusses the matter with her parents. Her father (still believing that David is a man from Oxford), sees no reason why the two shouldn't be married.
Soon after, Jenny's schoolmates are shocked when she is seen wearing an engagement ring in class. This soon catches the eye of both Miss Stubbs and the Headmistress once again, whom Jenny has some rather harsh words towards, before deciding to quit the school altogether.
Shortly thereafter, David arranges for a night out with Jenny and her parents. After stopping at a petrol station to refuel, Jenny checks the glovebox for a cigarette (where David usually keeps them), but finds just an empty carton. As she continues sifting through the glovebox, a series of letters catch her eye. When David returns to the car, she demands that he take them home.
After her parents go into the house, Jenny angrily chastises David for the letters...as they are addressed to Mr and Mrs David Goldman! Jenny is hurt by what has happened, and demands David tell her parents. When he still seems unable to cooperate, she says she will give him a few minutes alone, before she will come out and 'drag him in.' After this, David simply leaves without saying a word...leaving Jenny (unseen by the audience) to tell her parents the truth. Jenny also is sad in regards to how she has quit school and possibly lost out on going to Oxford.
Still knowing the address on the letters, Jenny visits the house (not very far from her own family's), where she finds a woman and a child. The woman soon realizes why Jenny is there, and claims she is not the first that her husband has tried to seduce.
Jenny soon returns home, where her Father says he will tell David off for what he did, but Jenny delivers some harsh words at her parents, who seemed perfectly happy with her marrying David, after some time before saying how important school was. Jenny then retreats to her room, when her Father comes to the door sometime later, apologizing for his actions.
Jenny then returns to her old school, asking to be let back in to repeat her final year of study. However, the Headmistress refuses. Jenny then goes to see Miss Stubbs, who is now glad to see that Jenny does not want to throw her life away, and helps her study and work hard to re-learn what she missed out on her final year in the school.
With her old teacher's help, Jenny is accepted into Oxford. The film ends with a narration by Jenny:
"So, I went to read English books, and did my best to avoid the speccy, spotty fate that Helen had predicted for me. I probably looked as wide-eyed, fresh, and artless as any other student...But I wasn't. One of the boys I went out with, and they really were boys, once asked me to go to Paris with him. And I told him I'd love to, I was dying to see Paris... as if I'd never been."