Rebecca Bloomwood lives in a flat in fashionable Fulham, London, thanks to her flatmate, Suze, being wealthy. Becky works as a financial journalist for the magazine Successful Savings, a job she says that no one who works there is very excited about, and they all say that they just "fell into", while in fact being unable to get better jobs. The job bores her. Becky admits to actually knowing very little about personal finance as she is thousands of pounds in debt as is evidenced by a run through of her Visa card bill. She becomes deeper in debt by uncontrollably spending on designer homeware, clothes and beauty products. The book emphasises that her cycle of debt is not easily broken, as, even as she is thousands of pounds in debt, Becky still receives letters offering her credit and department store cards. She often rationalises her overspending, for instance by referring to items as an 'investment' or necessary. Unfortunately for Becky, she considers things such as birthday presents for her friends as necessary.
On her way to a press conference held by Brandon Communications, Becky notices a sale sign in the window of the Denny and George shop. She sees that the scarf she has long craved for is on sale at a discount of 50%. Becky sees this as a unique opportunity but realizes that she has left her Visa card at the office and asks the shop assistant to reserve the scarf until she can retrieve her credit card. The assistant reluctantly agrees to hold it until the end of the day only.
Upon arriving at the press conference, she is greeted by a staff of Brandon Communications, who mentions that there's been some surprising news in the banking field and asks Becky her opinion on the news. Becky has no idea what the woman is referring to and has to feign knowledge. After the staffer leaves, Luke Brandon, head of Brandon Communications, realizing that she was feigning knowledge of what was happening, tells her that one financial group recently bought another, and it was recently rumored that Flagstaff Life was going the same way.
Halfway through the conference Becky is given another errand by her employer and realizes that she will not have time to return to the office for her credit card, but only needs twenty pounds more to buy her Denny & George scarf. She asks her friend Elly Granger if she can borrow some money, but Elly has none. Luke hears Becky ask for twenty pounds, and stops the whole Press Conference just so he can hand a twenty pound note to her, once she has made up a story of needing the money to buy a present for her aunt who is in hospital. Right after she has bought the Denny & George scarf she bumps into Luke Brandon and has to make excuses to leave, before he finds out that she's lied.
Later on during the week, Becky's flatmate Suze asks her to go to a restaurant with her and her cousins, including Tarquin. There, Becky sees Luke and his parents having dinner. The mother comments on Becky's scarf, and she blabs about getting it as a bargain. Then she realizes her mistake, and abruptly tells a suspicious Luke that her aunt died. Becky is mortified.
Luke runs into Becky after that and asks her to come shopping with him at Harrods. Initially she really enjoys shopping with him for luggage and goes up and down the shop wheeling around the luggage playfully, helping Luke choose the best purchase. After he reveals that the luggage is actually for his girlfriend, Sacha, Becky is very upset, telling Luke that she feels he's used her and not treated her with respect.
Throughout the story, a man named Derek Smeath, who is the manager of Becky's bank, is constantly trying to get hold of her so he can set up a re-payment schedule for her overdraft. Becky always has some excuse as to why she cannot send a cheque or meet with Mr. Smeath and his assistant, Erica. The excuses range from a broken leg, a dead aunt, etc., etc., until it becomes obvious to Mr. Smeath that Becky is quite unable to repay the overdraft. He becomes quite insistent upon setting up a meeting with her.
Suze and Becky happen to be flicking through a magazine and see a list of eligible millionaires. Tarquin is the fifteenth richest there, but also on the list happens to be Luke Brandon. Tarquin asks Becky out, while there Tarquin compliments Becky on her scarf and she continues the pretense that it's from her deceased aunt. She further embroiders that her aunt had set up a charity for children abroad to be given violin teachers. Tarquin writes out a cheque for £5000, which would solve Becky's financial problems, but she feels she can't possibly accept it, and painfully refuses. While Tarquin goes to the bathroom, Becky sneaks a look at his chequebook, wondering if a millionaire gets to buy a lot of lavish items. The content isn't extraordinary. Tarquin returns and Becky is sure he saw her looking at the chequebook. Eventually, Becky gives up trying to date Tarquin, as he is just not her type, even if he is very rich.
At this point her bank manager is trying desperately to arrange a meeting. Unable to come up with any more excuses, Becky goes back home to hide at her parents' house, lying to them when he calls and saying he is a stalker, Becky learns that her next door neighbors made a financial decision based on advice that Becky had absentmindedly given them and stand to miss out on thousands of pounds in a windfall resulting from a bank takeover. The bank had sent an offer of a carriage clock to people who would get the windfall, if they change their account to a different plan. The bank knew of the planned takeover and upcoming windfall, while the customers do not, but if they accepted the plan for which they are offered a gift, the customers will not receive the windfall. Becky is horrified by being partly culpable for her kindly neighbors losing out, and sets out to make things right by writing an article that exposes the bank's duplicity. The article is a success, and leads to Becky appearing on a daytime television show called The Morning Coffee. Unfortunately, Becky did not know that the bank was a client of Luke Brandon's PR firm. Luke became very angry with her, and thought she wrote the article just to get back at him for treating her poorly. Becky and Luke square off during her appearance on The Morning Coffee. After arguing with Becky, Luke conceded that she was right, the bank had defrauded their customers. So Luke Brandon announces that Brandon Communications will no longer be representing that bank. Becky gets a regular slot on the show.
Luke Brandon invites Becky out for a seeming business dinner at the Ritz Hotel. When Becky arrives at their meeting, business is not on the agenda and instead they eat their fill of the food, including a selection of all the puddings they liked the sound of, and then end up spending the night at the Ritz together. Becky has to miss yet another meeting arranged with her bank manager, but he writes and tells her this can be postponed, as due to her regular slot on television, her finances are now rosy. But the bank manager, Derek Smeath, will continue to keep an eye on her account.