One night, Ah Hui and Zihua get together and discuss the fear that their wives might be unfaithful. Michelle, Ah Hui’s wife works in a modeling agency and manages lots of good-looking male models. Of late, she has become cold and distant. Whereas she used to like Ah Hui to hug her, she now pushes him away. Xiao Tong is Zihua’s wife. She works in a hair salon and often comes home late in other men’s shirt. She would tell Zihua that she was out playing mahjong, and would slip into something more comfortable before coming home because it was too hot. Zihua proposes a ploy to test if their wives are faithful or not. Long ago, the two friends were experts at writing love letters that cause schoolgirls to go weak at their knees. Zihua suggests that they write anonymous love letters to each other’s wife. If their wives respond, it means that they are holding thoughts of infidelity. When Michelle receives her anonymous love letter, she is tickled but dismisses it as rubbish and throws it away. Xiao Tong is so tickled by her love letter that she laughs and cries at the same time. When the two men find that their wives did not respond to their love letters, Ah Hui is relieved but Zihua decides that they did not try hard enough. As a result, both men start putting in more time and effort into writing the love letters, thus neglecting their wives. Xiao Tong then decides to meet her secret admirer and tries to track him down. Meanwhile, Michelle slowly becomes curious and asks her secret admirer out as well. Both men become worried when their wives start to show interest in their secret admirers. However, Ah Hui dares not tell Zihua about Xiao Tong, and secretly arranges to meet. When Ah Hui tells Xiao Tong that they should stop seeing each other, she becomes angry. She writes him a letter that Michelle accidentally finds. An upset Michelle confides in Xiao Tong, who hides the fact that she is the person who had written the letter. She hatches her own plot to ‘help’ Michelle snare Ah Hui in the midst of an affair. At the same time, she wants to find out if Ah Hui will turn up. A meeting is arranged in a hotel room. If Ah Hui turns up, Michelle would know that Ah Hui has intentions to cheat on her. Xiao Tong watches in secret while Michelle waits inside the room. Zihua, who has gotten news of the meeting, turns up as well. Just as Ah Hui enters the hotel room, Xiao Tong barges in. Zihua, who has been following her, sees her with Ah Hui. An explosive argument ensues, and the problems plaguing the two couples surface, threatening to destroy their marriages.