The trouble with Mao, a neat and clean married woman, is that her sex life with her husband is not satisfying. One day, she falls in love with the kindness of a plumber who comes to fix her plumbing. Unable to bring herself to say it, Mao comes up with a way to make him fall in love with her: she purposely drops her keys in front of the man... The two of them become involved through the key. Their relationship gradually becomes more intense, and they become immersed in lust, which is called an affair...