Plot

Drunk, Archie sends a valentine to his best friend's wife. She sends one to her husband. He hides it so she disguises herself as a slut. Will he cheat on his wife - with his wife? Let us see what happens.

As part of a drunken bet with her sister, a happily married woman sends an anonymous Valentine's card to her husband to see if he hides it. When he does, what was a prank leads to a series of events and revelations that puts her marriage at risk, and leaves her looking for revenge.—Anonymous

After Alice Holbrook (Jennifer Love Hewitt), a happily married English woman living in Bristol, receives an anonymous Valentine's Day card with radish seeds in it, she automatically assumes the card is from her supposedly loving lawyer husband, Sam (Jimi Mistry), and that he is trying to be romantic. Alice works at the local NHIS as a nurse. When Alice and Sam meet at a gala, Sam says that he did not send her the Valentine's card and reckons that perhaps one of Alice's patients sent it.

In return, Alice decides to write an anonymous reply to her husband to keep the gimmick going, but only accidentally sends the card after a drunken night with her sister Felicity (Kate Miles). Felicity argues that all men are the same and would cheat on their wives if they had the opportunity. Alice is sure that Sam would tell her about a secret admirer, if he ever had one.

What Alice does not realize, however, is that her husband did, in fact, not send her the original Valentine's Day card; her husband's best friend and lawyer partner, Archie (Dougray Scott), did. Archie had written on the note "I will 'radish' you", which was meant to be funny and witty. Archie is working on fixing his sailboat and has been at it for a fairly long time. Archie is a passionate man and is willing to devote as much time as it takes to achieve the end result that he desires.

Sam receives the mail at home and opens the card in front of Alice. But then Sam leaves for office, without mentioning the card to her. When Alice's husband does not mention that he has received her card, Alice becomes suspicious that he is cheating on her with another woman. In an attempt to discover the truth, Alice sends her husband (she gets a new handset and a new number) a very provocative picture of her behind in lacy underwear. Alice wants to see if Sam calls back and to her dismay, he does. Alice picks the phone and pretends to be another woman with a deep, sultry voice who she calls "Anonymous." They end up having phone sex with Sam ejaculating on the other end of the phone.

Meanwhile, Sam and Archie are defending a famous football player Dan Harlow (Simon Webbe), who was caught having a threesome with a married couple. His wife Miranda has sued for divorce. The entire defense is based on Dan's manager Sharpe's testimony that Dan was with him that night till 10:30 PM and the hotel was 100 miles from his home. So, the incident could not have taken place at 11 PM as alleged by the couple. The prosecution proves that Sharpe was lying as he was at a dinner with the Railway Restoration Society and had his picture taken at 10:20 PM. Dan maintains to Sam and Archie that he was at home, while Miranda was out filming. Dan says that Miranda had revealed to him that she was pregnant, but after the incident she started saying that she did not want to bring the kid up with him.

Alice and Archie end up having dinner when Sam fails to keep the appointment, and they share the evening together. Archie, Alice and Sam used to study together at college. Archie tells Alice that he is taking up an assignment in Japan as Partner in a new law firm.

Alice continues the charade with Sam, and sends a card to his front doorstep, saying "Anonymous" wants to meet him that night. After her husband agrees to meet with "Anonymous," Alice becomes even more distraught, but continues to try and win her husband back. Alice borrows Archie's apartment that he used to share with his ex-wife, for her meeting with Sam. With heavy make-up, and a wig and a sultry outfit, Alice looks like a completely new woman. And she makes Sam wear a blindfold before he enters the apartment.

However, in the process, she discovers her husband Sam is already having another affair with a woman named Katya (Branka Katic) (as she followed him) and is now knowingly starting a second affair with "Anonymous" whom he thinks is a woman that he met in court during the Dan case hearing.

After breaking down over this fact, she goes to visit Archie in the sexy outfit she planned to woo Sam back with, and while Archie and her kiss, he assumes she is having an extra-marital affair with someone other than Sam and refuses to be a part of it.

Alice decides to forge ahead with her "affair" with Sam as "Anonymous," and while having supposedly extramarital sex with him, she removes his wedding ring from his finger with her lips. Afterwards, however, Sam declares "Alice is nothing compared to [Anonymous]" and that he has never truly loved Alice, and so she becomes very upset and flees the hotel. When she is running away, however, she runs into Katya, who discovers that Sam is not only cheating on his wife but also on her.

While Sam does win his big court case (by proving that the pictures of Dan in bed were digitally enhanced. Dan had a tattoo on his buttocks, while the pictures had no such tattoo), he returns home to find his precious wine scattered throughout the neighborhood and his clothes thrown in the street (all done by Alice), as well as Katya waiting at his house to tell Alice of their affair as revenge. When Katya sees Alice, however, she calls her "Anonymous," and so Sam realizes that Alice has been "Anonymous" all the while. Alice even shows Sam how she removed the ring from his finger to prove it. While Sam attempt to plead with Alice, she insists on a divorce and Katya walks out on Sam as well.

A little time later, Katya took her story as well as that of "Anonymous" to the press and so Sam's reputation as an upstanding lawyer has been ruined. Furthermore, the press exposes that Alice was, in fact, not having an extramarital affair as Archie previously thought. This realization prompts Archie to attempt to tell Alice about his feelings for her, but she cannot see past their friendship. Because of this, Archie decides he cannot get over Alice while still in Bristol, so he takes a job in Japan.

First though, he sends a goodbye letter to Alice, in which he includes "P.S. I hope you liked the radishes," finally letting her know that the original Valentine's Day card was from him and not Sam. Alice chases after Archie and finally catches him after a series of debacles at the train station, including him having to actually stop the train. They kiss and declare they love each other. Alice lovingly looks up at the man who really thinks she is "the perfect woman" and says "Take me home and radish me."